Re Americans being stereotypically rude or friendly, here's how I see it:
Americans *on holiday* are thought to be rude (push in, loud, brash, ignorant - in that no you can't use dollars, etc)
Americans *at home* are thought to be welcoming, friendly, etc
So for example if one was to go on a package holiday somewhere, it could well be "Americans" who were always complaining, etc. Go to an airport and you can always hear the Americans.
Now of course these are both very stereotypical, but might be the root of things. It could explain a few things, like so proud of home - so little travelled - welcoming to people to home because of pride - uncomfortable when overseas because so little travelled and hence overcompensating.
I guess what surprises me is the wealth disparity - how badly the "dirt" poor are paid and how a few are so so hungry for success, vs how comfy the middle class are; and, yes, the strength of religion, pride, and military strength + gun-loving when coupled with ignorance of the rest of the world (but no shame felt for invading parts of it - but WTFDIK about how the average American feels, I believe Bush and Blair both should be in prison for Iraq). The word that strikes me is *convenience* and how marketing is all about that (new car for only one easy biweekly payment!).
The sheer abundance of the US is amazing - the availability of good weather year round, amazing mountains parks glaciers deserts etc. You do literally have pretty much everything the rest of the world has to offer, all in one place.
I am very much looking forward to spending more time in the US over the next few years, I love reading road-trip books and vandwelling journals and the like.
*Edit* and how cheap housing is, and how cheap the mortgages are considering how long you can lock them in for... and how sad that there is such bullshit and so on that meant people got mortgages for more than they could afford with the teaser rates.. I mean come on, WTF really, how was that ever going to end well? Like.. the greed, the sheer 'capitalism' turned 'evil' - how cutthroat it can be. And yet combined with helpful guys in pickups giving you lifts and a place to stay and whatnot - the generosity of some people vs the greed of the system... It's a paradox, perhaps.