I think the same goes for exporting, even in the US.
I hear this many times and I can not know for sure as I do not work in that area, or have very much experience. But I doubt they even look at what goes out. When it goes out its not their responsibility anymore so they could just not care or even be happy that it is out, no matter what. The only reason to check what goes out would be so they can see if there is more, if its anything of concern and only if the senders adress is correctly given.
I doubt that they check what goes out in most states. I know one where they do, as they once caught a friend sending currency out, but china is very authoritarian