In Vietnam, the democrats underestimated the Viet Cong and we all know the consequence. Foreign policy should not be run on the basis of ideology, but only upon power relationship considerations. Accordingly, it's possible a democracy could be a power rival or a dictatorship an ally, depending upon the power balance considerations. If the entire world were comprised of only democratic states, there would still be power rivalries and wars where interests conflicted. You're still in a 60's mindset 49er.
Communism is dead.
China style of communism will be gone as capitalism and consumerism takes hold. Your fear of the spread of communism is silly, and for us to spend resources to contain it is a waste. Communism and other repressive forms of government can not survive the long run in a world of mass communication. Even countries like Iran and Afghanistan with their fundamentalist religious repressive governments will have to join the mainstream or be left behind in the backwash of poor, impovished nations, and will hardly be a threat to the rest of the world. They may commit a terrorist attack here and there, but if they become more than a nuisance, they will be slapped down hard by the rest of the world wanting to protect their status quo.