They check your bags and feet for dried dirt, maybe have you stand in a tray with chemicals to destroy anything nasty on the bottom of your shoes, and check your country of origin against a list to see just how bad it could potentially be.
US Customs generally speaking aren't that bad. It is US immigration which are authoritarian nutjobs (and the TSA).
US Customs seem to be mostly interested in FACTS, immigration and the TSA seem to be mostly interested in if they like you as a person and if you treat them well.
With food things are unpredictable. I am in the habit of declaring everything up front (and occasionally I do find out later I missed something) but it's rare that I have stuff confiscated and when I do it is a surprise to me. It isn't so rare that they look through and itemize what food I am bringing with me.
The last time I had stuff confiscated it was during the bird flu scare and it was dry instant noodles with some sort of dry chicken flavoring in it. I guess chicken = bird flu......
US Customs generally speaking aren't that bad. It is US immigration which are authoritarian nutjobs (and the TSA).
US Customs seem to be mostly interested in FACTS, immigration and the TSA seem to be mostly interested in if they like you as a person and if you treat them well.