Nazism - A bunch of Germans get together and decide that Germany's the greatest country in the world. On a wave of nationalistic intentions, they manage to take over the government. In order to gain more resources, they get the international community to fall into a cycle of appeasement which, despite Chamberlin's words, does not lead to "peace in our time". When the free land gig stops working out for them, they invade most of Europe and are only eventually fought back in a two front war when America provides too many soldiers for the Germans to shoot at on Omaha beach and the Russians withstand the siege of Stalingrad.
Fascism - Mussolini decides to restore the glory of ancient Rome and attempts to forge Italy into the greatest nation in the world. He allies with Hitler and loses big.
Communism - After centuries of oppression necessary to the Feudalistic system, a couple of Russians organize the factory workers and lead the nation through two revolutions. One in March which brings an end to the Romanov dynasty and brings in a provisional government of moderates. One in October which forces the Mensheviks out of the country and brings in a radical government. After some leadership shuffles, they fight Germany to a standstill in World War II and then decide that since they're one of the largest nations in the world, then they ought to help the rest of the world by foisting communism on them. The U.S. stands up for the rights of the other nations mostly through the Marshall plan and enters a cold war with Russia consisting of building an excessively large military and taking turns threatening through political posturing ("We will bury you", "the evil empire", and so on), weapons tests (Most notably the Tsar Bomba), and espionage. The cost of keeping up with the U.S. eventually catches up with Russia, forcing another revolution and change of government. The U.S. comes out of it with a huge national deficit, some unpopular wars, and some scandals which are difficult to pin down.
Now which of these is more like the Nazis, fascism, and communism?
Islamic terrorists - Completely without a nation or nationalistic feelings, the U.S. is branded as the Great Satan for certain unpopular actions in the Middle East (e.g. the invasion of Iraq, aid to Israel, and so on). In a bid of desperation, they wage war through guerilla tactics and terrorism.
America - A president is controversially elected. After a stunning terrorist attack, the country bonds together as a nation. The legislature begins passing things like the Patriot act and sing "God Bless America" on the capitol steps. A president who had been believed likely to be a one-term president steps up and begins talking about how America is a great nation. He leads us on a justifiable war followed by a very unpopular war, breaking promises about nation building, and riding roughshod over the international community. He wins a second election controversially. He continues with his policy talking about a mandate and how more people in history voted for him than any other president. He conveniently ignores that roughly the same number voted against him as well.
I suppose irony isn't dead after all.