Americans, the citizens of the United States of America, have a long tradition of anti-imperialism. After all, our 13 original colonies rebelled against the British Empire in 1776 and established a "novus ordo seclorum," in which, in theory at least, all men are created equal.
Hypocrisy, however, was in no shortage among America's founders, who went off a conquering as soon as they got the rabble they whipped up for the Revolution back under control. Jefferson, Jackson and the lot did not consider Native American nations to be real nations, hence there was nothing imperial about taking their land. Nor was there anything imperial about trying to take Canada in 1812, since the Canadians should have had the good sense to toss off the Brits all along.
Well before World War II began the U.S.A. had become one of the great imperialist powers, behind Great Britain, France, and the Netherlands, but ahead of Spain, Italy, Germany, and Japan. We ruled the Philippines, Hawaii and Puerto Rico directly, and maintained puppets in many Western Hemisphere nations. Despite that many Americans, including presidents like Franklin Delano Roosevelt (FDR), made good anti-imperialist speeches.
FDR and crew were against British, French, Dutch and Japanese imperialism. Those imperialists prevented U.S. commercial penetration of their domains. It is possible FDR's rhetoric even fooled Ho Chi Minh, the leader of the Vietnamese struggle for independence.
Before World War II what we now call Vietnam was divided into three parts [if you must know: Tonkin in the north, Annam in the center, and Cochin China in the South], but all were essentially one big colony run by the French, who also ran Laos and Cambodia, the whole region being referred to as French Indochina. The French were vicious in their exploitation of Vietnam, killing and starving people to death in numbers that, had the French been Communists, would have got them in big trouble with both yesterday's and today's American propagandists.
Ho Chi Minh, aiming at independence, was dealing with a remarkably complex situation. Although he was a communist, he was also a nationalist whose first goal was to kick the French out. There were also Vietnamese nationalists who were not communists; most allied with Ho, but some saw themselves as future rulers, and so either fought the French separately or even put energy into sabotaging Ho's organization, the Viet Minh. The nationalists bickered among themselves, but there was a lot of bickering in the Viet Minh as well.
Before World War II the French kept alternating governments between conservatives, who had no sympathy at all for the Vietnamese, and socialists, who in theory had sympathy but who nevertheless opposed independence for Vietnam. Ho and his diplomats negotiated with all of them. Ho was willing to accept independence within a French federation. He was a moderate and worldly guy who had lived at times in France, the United States, and the Soviet Union, before setting up his headquarters in southern China.
Where and when World War II began depends on who you ask. Japan started styling itself the America of Asia in the 1930s. Japan was one of the few independent Asian nations, it had a democratic and militaristic government (just like the U.S.), and it asserted its own equivalent of the Monroe Doctrine. Monroe told the European imperialists to keep their hands off the New World (western hemisphere). But later U.S. presidents grabbed as much territory as they could and frequently sent in the Marines to "restore order," often by appointing a dictator.
Japan told the European imperialists it was time to get out of Asia, and Japanese leaders were very interested in the restoring order game. The most disorderly nation in Asia was China, where a combination of internal weakness and predatory tactics by Europeans and Americans had left a state of chaos characterized by warlord rule, famine, and economic distress. Communists had set up their own Chinese state in the northwest, while in theory Chiang Kai-shek and his Kuomintang (Nationalist) Party "governed" the nation as a whole. To describe the mess in detail is beyond the scope of this essay. The Japanese, on the other hand, had built up industrial and military capabilities sufficient to defeat both China and Russia in earlier wars.
The Japanese went about restoring order in China, meeting the same kind of resistance the U.S. met when restoring order within the Monroe Wall. No American President liked the Japanese out-competing the U.S. in China, but in particular FDR did not like it. The "Delano" side of his family had made its fortune running illegal opium into China, and Roosevelt backed the Open Door Policy, which allowed every imperialist nation to pillage and rape China's economy, as long as new official colonies were not established. Roosevelt berated the Japanese and sometimes even British, French and Dutch colonialism in Asia, but note he did not grant independence to the Philippines, a U.S. colony.
Pretty soon there were 3 major governments of China (many more, if you count the war lords who ran with Chiang but obeyed no one but themselves): the communists, the Japanese puppets (one in Manchuria, one in Coastal China), and the increasingly irrelevant Kuomintang. FDR decided to prop up Chiang, who had married a Christian, American-educated banking princess. Money flowed and ammunition flowed to Chiang, but most of it was diverted by his corrupt cronies or Madam Chiang's family. So FDR sent the U.S. Air Force to fight the Japanese. In order to avoid going to Congress to ask for a declaration of war (the Republican Party was opposed to war back then, and enough Democrats were for peace to kill such a request) the U.S. Air Force in China pretended to be volunteers in the Chinese air force. They were known as the Flying Tigers.
Meanwhile, back in Europe, Adolf Hitler's German army had defeated the French Army. The French fascists, led by Petain, made a deal to rule much of France and all its colonies from Vichy. The Japanese then demanded and got the right to station their troops in Vietnam.
No one was helping Ho and his comrades very much. After Pearl Harbor, Chiang and the Americans were willing to give Ho limited support as long as his ragtag guerillas fought the Japanese. The Russians were too busy with their own problems to help. The Chinese communists provided some training, but they had to fight both Chiang and the Japanese, so their support was minimal.
Ho Chi Minh and the Viet Minh did the best they could during the war years. They organized a vast underground network and a Provisional Government. The French killed as many Viet patriots as they could, and the Japanese did too. [Many native leaders in the Philippines cooperated with the Japanese, as did Indonesian and Burmese leaders, and in turn these nations were granted independence. It is not clear why that strategy was not followed in Vietnam.]
When FDR died and President Truman vaporized Hiroshima and Nagasaki the Vietminh thought the time for Vietnamese independence had finally come. Instead, since the U.S. was busy occupying Japan (a goal of U.S. imperialists from at least 1850), the allied imperialists somehow decided that the Chinese would occupy northern Vietnam and the British would occupy southern Vietnam. They were to ship the Japanese soldiers home, but what would come next?
The French wanted Vietnam back! The Chinese considered keeping North Vietnam, but Chiang could not really spare the troops since he was planning to wipe out the Chinese communists. The Cold War was already on, with the U.S. and British Empires demanding free elections in Eastern Europe (held by the Russians after defeating Hitler) and the Communists demanding free elections in France and Italy, plus the deposing of General Franco from power in Spain. Similarly, free elections were all the rhetorical rage in Vietnam, but just in case the imperialists refused to cooperate, the Viet Minh seized what territory they could, which included most of Tonkin. The local remnants of French fascism not being up to the task of fighting, they encouraged the Japanese, who were now POWs, to fight the Vietnamese independence forces!
To wrap up an already long story, while Ho negotiated with the new government of France organized by Charles de Gaulle, the French got enough material from President Truman to put together an army and reinvade Vietnam. Truman felt that French imperialism was better for the U.S. than Vietnamese independence probably leading to communism.
So the Vietnamese had to fight a long war with the French, and when they won they only got North Vietnam (the deceitful French agreed to nationwide elections, then used an interval of peace to set up a puppet regime in South Vietnam, which the U.S. soon came to equip, finance, and generally pull the strings of).
Sadly, although imperialism has taken on forms different from the colonies of the past, it is still a major part of the world order today. As I write this the French are "helping" African nations by sending in the Foreign Legion again. America has never given up the imperialist game; Barack Obama has approved plans to establish U.S. military bases in almost every country in Africa.
Inside the U.S., the anti-imperialist movement is weaker than it has been at any time since the American Revolution. People just don't care, they don't know the present day facts or the historical facts. American citizens don't understand how imperialism enriches our elite, sucks the blood out of our working class (and even the middle class), and is largely responsible for the impossible-to-pay-back federal debt.
But hey, won't Apple being coming out with a new phone next year? Shouldn't that be what we are focusing our attention on? Or Lady Gaga? Or World of Warcraft?