I've never been to the US, because I've been scared of these things, for decades, after reading stories about it. I've traveled to Canada and Mexico multiple times, but one time I made the mistake of having a connecting flight in Florida (first and last time).

As expected, I was interrogated by police-looking people about my motivations, yelled at by some other ones to walk faster and use some machine faster, and almost missed my connecting flight because of the "some questions", even though I never actually intended to enter the US, since I was on my way to Mexico.