Weird. I have never had a pleasant experience with US customs. They are usually not unpleasant either, but they’re never friendly or even more than vaguely polite.
(I say “usually” because my wife was once told off quite rudely when she went through the visitors line as a permanent resident, because she wanted to help and translate for visiting family members she was with.)
The worst part of the experience is knowing they will not hesitate to fuck me over if they decide they want to, and I have little recourse. They can’t keep me out of the country, but they can screw me up for hours or days if they want. They can keep my wife out of the country arbitrarily, and the only fix there would be a lengthy and expensive legal process with no guarantee of success.
It’s minor compared to the hypothetical example of being imprisoned or executed on false drug charges, but my point isn’t that US immigration isn’t equivalently bad, but that I felt and experienced no menace whatsoever from Chinese law enforcement.