US customs (technically either CBP or ICE) do have the authority to inspect your external hard drive and other electronic devices and there are a few criminal cases based on such searches. But they obviously cannot systematically inspect all devices or HD people carry through the border and would not be primarily looking for illegally downloaded music (if that's what you mean).

Data obtained by the ACLU suggest that such searches remain exceedingly rare. Obviously, none of this positively guarantees that you won't get in trouble but thousands of people do the same everyday.

US Customs check External hard disk
I have a maybe (3 lb?) block of Philadelphia Brand Cream Cheese. I just cut into it for the third time and noticed several pockets of what appear to be to be water in the middle of the cheese. I've never seen that before and wonder if anybody knows what causes it. It's well within its expected freshness time, has always been refrigerated and carefully wrapped. The pockets of clear liquid range from 1-2 square centimeters, and are right in the middle of the cheese. The cheese tastes and smells perfectly normal. Can anybody say what this is?
