If a USA citizen is a victim of crime in a foreign country. Can he take legal action once he's back in the states? Or are the legal fees too prohibitive for those of us who aren't rich making it best just to forget about it?

You would have to take any legal action in that foreign country.

At least that was what we (Canadians) were told a few years back when it happened in America. Therefore, we decided to just drop it since the cost would outweigh the benefit.

The police of that county would investigate and attempt to arrest the person who did the crime just like in the US. If you believe you have a civil case against them ( but also remember laws in other countries don't work like the US) you would have to do all of the action in that nation.

If you're over seas and are the victim of a crime or tort, go to the police immediately. If the police do not help you, then your next stop should be the American Embassy in that country.

If you can, persuade the police to at least file a report with as much detail in it as you can give them/make them put in. This way, if they fail to live up to their empowerment (to serve and protect), then you have some sort of bearing when you contact the embassy or your own local law enforcement in the county/city you reside in here in the US.

Good luck