I have to admit some border crossing incidents[1] are what I would imagine entering North Korea would be like, not the US.
[1][10min audio] https://www.youtube.com/watch?v=MDYMw1p8s9M
[1][10min audio] https://www.youtube.com/watch?v=MDYMw1p8s9M
Ex: "what shops are you planning to go to". It's fine to answer "I don't know yet". They're just testing behaviour. If you start being defensive or aggressive, pretend to know their jobs better than they, etc, it's suspicious. Although yes, in general, the US agents are really bad at doing behaviour testing.
Anecdotal: Last year, I crossed the border a few times by car, visiting a friend I met on Tinder. I completely got away with it, giving honest answers at the border. Recently met someone else (a girl) who was stopped and accused of prostitution for doing the exact same thing. :/
You may not understand quite how much most Americans hate CBP. I use "hate" here deliberately. It represents the worst part of our government and a codification of our racist laws and culture even at the best of times.
They find a way to weaponize ignorance and shame people who are different at every turn. They have tackled people and held them at gunpoint for LED shirts, they've publicly shamed women for having vibrators in their luggage, they've delayed flights because people speak Tolkien's elvish leaving comicon.
And their definition of sincere risk? Brown people or people who are different. They can detain Americans and non-Americans alike without due process and stories report they do just to make a point.
And the worst part? They are bad at their jobs. The FBI is a problematic institution as well, but at least they can point to data that suggests they're doing things here and there to actually foil people who genuinely want to cause domestic problems.
Even conservative Americans hate the TSA and CBP face to face. We're all scared of them, because we know they're stupid and bad at their jobs but terribly powerful.
No, because you didn't do anything wrong.
Border crossing is not a crime, last I checked, despite the best efforts of some to make it feel that way.
Contrast that to this (6min): https://www.youtube.com/watch?v=tV-wgZBGfCo
None of those stories are that important in and of themselves, it's the whole normalized atmosphere of fear, guilt and almost agony that I don't understand.
Of course there is going to be someone who reacts badly, but you would think that they have professionals at the border that know this, from what I've seen when disembarking in London there are people who know how to handle these things. I've seen the same situation being descalated in 10 seconds.
I'm guessing there is little pay and pride to be had for a border guard in the US, so little incentive for being anything else than a git.
However, Canada can be just as bad. Bottom line: know the law, be polite/calm, travel light, be honest but keep answers at a minimum. Unfortunately, since I travel often for business, that means I've spent way too much time at social events exchanging about travel tips, rather than actual productive conversation. It's also silly that we're adding barriers instead of removing them. What a waste :(