How does the FCC catch illegal HAM radio users?

I don't know anything about HAM radios. But I've heard that there are serious penalties if one for example grabs a HAM radio and starts saying all kinds of non-sense on all frequencies.

But if radio wave can bounce off the "I forgot what it's called"-sphere. And can originate and travel all over the world. Then how on earth (pun intended) does the FCC find and give citations to people that are using HAM radios illegally or are not complying with HAM radio rules?

By the way. What are some of the fines the FCC can impose on someone other than revoking your license?

What about aliens? If signals are sent from another planet, does the FCC try to track them down to give them a citation too?!

Why the interest in operating in America?