Firstly, let me go to another topic previously mentioned - the dictators of Europe pre-WW2.
The Portuguese dictatorship was entirely unrelated to Hitler, at least, in its creation, as was the Italian dictatorship, and most of the dictatorships in Europe. The only dictatorship to form that was as a direct result of Hitler's intervention was Francisco Franco, Regent of Spain. However, with the exception of Portugal, most of the dictatorships were either allied to Germany (Italy, Romania, Bulgaria) or conquered by Germany/Allies (Poland, Yugoslavia, Albania, Greece), or both (Vichy France).
Now, to wholly understand the US's role in the Second World War as it pertains to Europe, leaving out in entirety the Pacific theater of the war:
In mid 1940, at the height of the Battle of Britain, Franklin Roosevelt ordered the creation of an agreement of bases in exchange for American military equipment, which Britain immediately took up. This material aid caused Hitler to argue with Roosevelt over this, and ordered attacks on US shipping to Britain, leading to the little-known Atlantic Conflict, a police action from December 1940-December 1941, in which the US Navy was ordered to
Take all actions necessary for the protection of Anglo-American trade, including, but not limited to, the nullification of German submarine control of the Atlantic ocean. In effect, Roosevelt went to war with Germany in December 1940. These conflicts between the US and Nazi Germany in the Atlantic for a year before official American entry into the war are always forgotten, and overshadowed by Pearl Harbor, and the rapid attacks on Samoa and the Philippines by the Japanese, a year later. Nazi Germany and the US, however, had been unofficially at war for a year before the official American declaration of war.
Now, let us point out that many Frenchmen supported Petain's dictatorship. While the vast majority, after the war, claimed to be part of the Resistance, get real: there is no way that such a supermajority majority of French were members of the resistance, yet did not manage to nullify German control in ANY part of France for the four year occupation. Many Frenchmen, both in France and in the colonial areas, supported Petain, and, by connection, the Axis. In effect, France was an Axis power, for all intents and purposes, until D-Day. French corroborated with the Nazis in the occupation of Morocco, Algeria, and Tunisia (all French-controlled at the time). There was a French-supported Nazi occupation of Tunisia, where hundreds of Jews were massacred as part of the Holocaust, not to mention several thousand in the other French territories, where the Nazis did not have the manpower to do it alone, and, therefore, the French were doing it themselves.
Now that we've shown French corroboration with the Nazis, one can see that the US was NOT allied with France in World War II - just the Free French, who had far less support than popularly believed. In effect, it was an Anglo-American alliance, in treaty with the Soviet Union, that defeated Nazi Germany. Britain, however, did not really have the industrial base nor the population for extensive actions. Therefore, basically, without American assistance, even though Britain would have likely held off the Germans, the European Union, today, would exclude Britain, and be dominated by Germany, in all likelihood. The Soviet Union, also, did not have the material to defeat the Germans, even working with the British, and, though, again, would probably have managed to hold off the Germans, Germany would still end up a dominant state with eventual puppetting of Switzerland and de facto control over Sweden likely achieved, possibly even over Ireland as well.
Therefore, the United States was essential to Allied victory in World War II, and was far more involved, far earlier than even Americans realize. Now that I've totally thrown off the topic at hand, we can now argue, and then decide to be happy in our diversity