I was born and raised a US citizen. My wife is Canadian. I spent 21 years in the Air Force and 24 years with GE Aircraft Engines so we have lived all over the world in our 42 years of marrage. We have been treated badly and nicely in many countries.
The US customs are the worst when it comes to intimidation. These people are low wage, low educated people who have been given a job with unlimited power and it goes to their heads. They get to wield power over all the tycoons, CEO's, and anyone else. But I have found if you keep your cool and have the proper paperwork, you will be admitted into the country.
"But I have found if you keep your cool and have the proper paperwork, you will be admitted into the country." Let me give you another take on this sentence - I'm not bitching, just remarking.

I'm Keith, my wife's Marie, you may have heard of us from elsewhere in this thread.
Last summer we flew through Philadelphia en route to AZ to collect our rig. We'd had a few problems on other occasions elsewhere so we went as prepared as we could with appropriate documentation to show that we could support ourselves when in the USA. We also had documents to show that we owned property in the UK thinking that would indicate we had 'compelling reasons to return to our homeland' (or however the official jargon put it). Put simply we wanted to demonstrate that we understood the rules and had no intentions of staying illegally.
To make things easy, Marie went to the immigration desk while I stayed behind 'the line' to wait my turn. After a short while I could tell she was having a bad time. Eventually my turn came and I was told that although we had come prepared with documentation (quote)
"she was far too well prepared" and next time we might be refused entry. But we got our I-94s and staggered away from the desk.
Shaken and upset, but relieved we were in the USA, we comforted one another. What sticks in our minds - and particularly in Marie's craw - was the terse accusation by the official that Marie "was far too well prepared"
What does one do for the best? We decided that in future we'd keep any documentation with us but not in sight. So far, so good.

It's not changed our love for the USA and almost without exception we've found its citizens are open, friendly and welcoming. But oh what a shame the system and its servants treat honest, law-abiding folks like ourselves as if we're not....