I drove across TX in < 8hrs, IIRC.
When I say "Have a nice day" it isn't fake.
Americans are so different from each other. Laid back Californians don't understand uptight New Englanders, but they share political instincts & both look aghast at southern and 'western' conservatives. Westerners are more resilient & crotchety; southerners have a huge chain of social codes that outsiders can never understand.
Oregonians are the most eccentric people ever (say my Californian cousins who moved there).
I could lean towards making these sweeping generalisations....
Brits used to highly value intellectualism & expertise & training & process, even as Americans deeply didn't (see GWBush presidency). Post-Brexit, I'm not so sure; Brits became sick of experts and populism is huge in UK. But American current embrace of populism is more naked, more zealous and wide-ranging.
Americans don't worry how much they have offended you but you are so offended you can't even be bothered to say so; traditionally we didn't have a culture of resentment or envy (but see Trumpism for how that's changed, now resentment is well-in fashion). Americans don't have mega-angst about what you aren't saying that are your true feelings. We assume you'll take care of your own needs and what you say is what you mean. We also aren't in love with process & procedure to fix problems.
The American dream has a sharp double edge, it implies it's your fault if you didn't succeed. I quite prefer British "Life can be unfair and suck" resignation.