it doesn't mean he's knows anything about other areas. Will Rogers said it best decades ago, "Everyone is ignorant, only on different subjects." Some people have a hard time accepting their own ignorance in areas outside their range of expertise.

Not speaking about Chomsky in particular, there is a tendency among some highly educated people to think their expertise in one subject means they're experts on all subjects. It's a form of arrogance that quite often leads to spectacular failure. I have no idea about Chomsky's particular bias against the US and quite frankly couldn't care less.