<During the Cold War, there was the Soviet armed force that restrained Hungary and Tchechoslovakia from getting more freedom.

I don't even understand this statement. Elaborate?

The only thing restraining tyrannies are their own tyrannical governments, not the US.

If the United States had decided to stay home, and say to hell with Europe after WWII, you would now be a Soviet citizen. Politically unpleasant, maybe, but true.

Look at Algeria, Iran, Iraq, Lybia, etc... None of those countries can afford to project their tyranny away from their borders and their power is limited to their own countries. What can they do about the US?

I wasn't talking about the U.S. being directly attacked in my speculations. I was talking about neighboring nations, and despite what you say, countries like Iraq and Libya have already demonstrated a willingness and ability to attack and invade their neighbors with the objective of taking over territory. Here's a little bit on Mideast conflict from our good buddies at Wikipedia.

Dictators and conquest go together like peanut butter and jelly. Don't kid yourself.