Been to the US, have worked there and have worked with lots of Americans over here in the UK. Most of them are nice people, some of the kindest most educated people I have ever met, but....
In Europe we have certain rights such as free speech. We believe that you have the right to say whatever you want but are expected ( kind of unwritten rule ) to try not be be blatantly offensive. Obviously we have dicks over here but they are rightly confronted by the mainstream and marginalised. The debate on evolution pretty much ended when Life of Brian came out.
In America you have similar rights, however many Americans believe that if you have the right to something then YOU MUST DO IT. TO THE MAX. ITS YOUR RIGHT. Freedom of speech becomes a REQUIREMENT to be rude, confrontational and abusive. You get lawmakers making blatantly racists statements that in Europe would finish their career. To the American mindset calling Obama a "dirty brown communist" is not racist - its freedom of speech. Its my damn right to say whatever I want no matter how offensive or factually incorrect it is.
Allowed to own guns? Yeah I want a fucking machine gun. No I want five. And a flamethrower. Just because.
Like big cars? Yeah I want a fucking humv. Climate change is bull. I am going to burn even more gas.
America has this strange "its my right to be a fucking ignorant arsehole" attitude. It's everyone's right to be a dick, but in the US its something a lot of people aspire to. Being an offensive loudmouth who talks big, shouts loud, insults everyone, never takes advice, never listens to the other side, etc, is considered a sign of strength.