In Tokyo I was through customs so fast I wasn't sure I was through.
Last time I entered Jamaica I was shaken down. After going back and forth for a few minutes I realized it was a shake down and simply asked him "how much?" $50 later and I was on my way. To make a long story short I had brought a few gifts for friends who were meeting me there and the customs agent claimed I was bringing items into the country to sell. Um yeah, I'm selling 4 towels?
In and out of Costa Rica was interesting. When I went I only took a backpack and surfboards. They didn't say much entering the country and only checked out the surfboard bag. Leaving the country they searched everything multiple times prior to leaving (once at security then again plane side). They were all very polite though.
Admittedly I don't do a lot of international travel but I've never had any problems entering the US have always answered the 1-2 questions with yes/no and "I'm glad to be back."
Every country is different, but coming back into the US is a uniformly annoying experience. From my experiene, US Customs/Border agents are at the very least lacking any sort of friendliness with some sort of powertrip being the norm.
Given these are some of the first people visitors to this country encounter, I would hope they would be friendly and professional rather than surly and on an power trip.
Every foreign country I have been to (mostly Europe and Canada) has been friendlier and more welcoming than every single instance that I have had in dealing with US customs upon re-entry. And, for the record, I am in the "here's my passport" and answers questions crowd.
And I have experienced the exact opposite when entering US. The agents have always been friendly and courteous. I wonder if it has to do with what airport you enter the country from. All of my international flights end up going through ATL.