Is America fake or is Britain hostile?

Recently I visited Hollywood on a school trip this February. Besides the huge size differences apparent there (super large vs super skinny was certainly something that came to mind), I was amazed by how polite and courteous Americans are. Compared to them, we're rude, obnoxious and extremely hostile towards one another.

One of the "rules", you could put it, of being a true gentlemen is to hold a door open to let a woman pass through. This is treated as a kind gesture, but should it really be treated as a big thing? Surely it's one of those things you instinctively do if you're a nice person? I think that's the difference between the two countries: When a Brit does something nice, its 'good deed of the day - done'. Yet when an American does it, they just get on with their lives and perform the same thing countless times the same day.
Everyone there is so jolly, so upbeat, so refreshing, that it really gave me an insight into what life would be like if us Brits were like this 24/7.
Fair enough, there were a few people that dimmed this perfect image of American citizens - one security guard at LAX was extremely impatient, constantly banging on his prison-esque cubicle he'd call a workspace for the next person to go through customs whilst shouting "C'mon ma'am!" numerous times. But this contrasted to others such as the baggage handler who noticed we were British (which, for some reason, most took a liking to - again different to us who, for the best part of the general public, would wonder what these 'yanks' are doing in England). This woman made a joke about us, saying who she thought was trouble, who to watch out for, pointing accusing fingers in a light hearted gesture at a few of us.

Everyone in America is so confident, so outgoing, that it makes me wonder why we can't be the same. Sure, America is a superpower so in a way you almost expect every single American to be right up in your face - I agree, some were quite pushy and hard to get rid of in certain places - but it's funny that not even a quarter or so of us can meet their standards in this department.
Why?