If as many as 1/2 of the population are not brainwashed, I would be very pleased (and surprised). Unfortunately I think most people are fairly brainwashed. Not just in the US, but everywhere really. Some countries have it worse than others. America has it pretty bad I would say. And a big reason for that is apathy. They are comfortable just trusting the mainstream media, CNN, MSNBC, ABC, CBS, NBC, FOX, etc. They are not trusting or comfortable with news sites like Al Jazeera, RT, BBC, Le Monde, etc because those sources are "not American." Most people are extremely provincial and they get their information from very limited sources.

I should add, I think there is a spectrum of brainwashing going on. Some are so far into not being brainwashed that they go over the edge into conspiracy theories and so on. The other extreme is, of course, the guy who watches FOX "news" 24/7 and thinks everything else is "librul propaganda." No one can ever know all the truth about everything, of course.