First, I'd like to point out, there is an American Communist party. They will never stand a chance though.
Communism can literally turn a mideaval country like pre-WWII Russia into a world superpower. However, as we all have seen, it only lasts so long before it evolves into a mix of capitalism and communism. I'm not sure the Soviets really made third world countries any better despite giving away tractors... there are now millions of post-soviet AK-47 and RPGs available to the weak governments of these 3rd world nations for dirt cheap. Factions in these countries destroy each other and hurt the population as they vie for power. Many people who have dreamed of living in a communist country go to one and end up hating it. (Lee Harvey Oswald for one example.) I am not for communism, but I wish to someday study the history of various societies such as the Soviets.
As for shutting up about our "Democracy," I know that right now it isn't perfect, but at least we have a chance of changing it without shedding blood. It's just a matter of the masses doing something about it.