Americans are very friendly and open the first time you meet them. Happy to be your best friend. Then they get to know you and evaluate you. It at this point that they decide whether you are going to be their long term friend or some unfortunate acquaintance. The Brits otoh warm to people more slowly. This explains why Americans open up immediately about their marriage and fluff in their navel.
I imagine this can be explained by the past. The country as it is today was created very fast and people needed to make allies immediately.
Then if we look at the sort of people, who went there. A significant proportion were the ultra religious escaping persecution. Many of these people were quite radical thinkers on the fringes of society. People from different nations emigrated there in droves for the same reason both in the infancy of the country and more recently. It therefore isn’t surprising that Americans are vastly different.
I think calling themselves “Americans” interchangeably is to create some kind of cohesion. Religion also creates cohesion. The president has to believe in God and their politics are completely entangled in religion.
Then of course they have the amendments, which allow extremists to assemble such as far right groups and the and the dubious right to bear arms.
Yes, the Americans seem to be very much into therapy. But the reality is that they only look after the mental health of those, wealthy enough to pay for it. And even then there is a rigid framework to adhere to, a mould to fit into. The frequent high school shootings bear witness to this inflexibility and pressure on children to conform.
The Brits otoh aren’t expected to conform in quite the same way. Personally I’d rather be a sweary Brit accepted for my quirks than expected to be an all American behind my white picket fence. But that’s what I’m used to.
However I am sad that patriotism in this country has died. It is a shame we cannot go back to the post war feelings for our country but in a new era where we realise that England and Britain (and the U.K.) aren’t synonymous.