I haven't traveled that extensively, but every time I've entered a Schengen country with nothing to declare, I've been able to walk right in after getting my passport stamped.
Every time I've returned to the US, however, I've had to go through an exhaustive baggage screening and pat-down before I could even board the plane, and then stand in line for half an hour in Immigration once I got back, filling out an entire form to declare that I have nothing to declare, and answering random identity-verifying questions from an immigration officer. I feel tired and uncomfortable just thinking about it.
I'm one of those lucky people that is apparently innocent-looking enough that I never get messed with by customs. And I've been through lots of weird customs checkpoints.
Returning to the US you have to fill out that annoying form on the plane but other than that it's just a rubber stamp
China is similar. I had to act like I was entering the country and leaving right after just for a transfer flight/layover. They're the only place that detected the belt buckle and cared about shaving razors.
i haven't either, but my experiences were actually the opposite.
i usually get searched when entering a foreign country because i have snacks on me or something. i usually have very little hassle when returning to the US, never been searched (knock on wood).
Returning from Oslo, Norway
Immigration officer: Why were you visiting Norway?
Me: I was there visiting some friends.
Immigration officer: Why do you have friends in another country, sir?
Every time I've returned to the US, however, I've had to go through an exhaustive baggage screening and pat-down before I could even board the plane, and then stand in line for half an hour in Immigration once I got back, filling out an entire form to declare that I have nothing to declare, and answering random identity-verifying questions from an immigration officer. I feel tired and uncomfortable just thinking about it.