I grew up in the 80s in the Soviet Union. And the thing is, we never believed their propaganda because it was too ridiculous. Everyone was laughing at the bullshit they heard on the radio and TV. True believers have disappeared probably the the mid 60s or so. Even defecting spies had stopped using "ideology" as the reason for their defection it was too unbelievable.

Likewise might happen in US. It seems two things has happened already. They stretched propaganda vs reality difference too thin. And the Internet.

It becomes harder to keep a straight face telling others about freedom, privacy, free market, human rights in light of news about torture, drones, spying etc. Also, without an ability to get access to alternative media and if Fox was the only channel available many would still thing this country was God's gift to humanity. It is just the pesky Internets that lets "domestic terrorists" like Occupy organize and share idea. Pesky little extremists forums like /r/news lets people discuss issues outside the mainstream media.

On another note. There was an old joke from back in the 90's. "When Soviet Union fell, we found out everything they told us about Communism was a lie. And everything they told us about America was true".

Good counter-propaganda after all, is often not telling lies just telling the dark truth the other side is trying to hide. In other words I doubt the Marshall Plan America is a good ol America or is it the America that still believed in segregation, raping South American countries for profit, installing brutal dictators in South East Asia and so on.