Plenty of countries can care less if you're a spammer, especially if your only spamming other countries.
You can easily setup thousands of servers anonymously in another country and spam the hell out of the US.
Since your info is private, the US cant prosecute you. All ISP's can do is blacklist your IP's and domains, which of course you can always replace over and over.
Most people don't have the money, the drive, or the knowledge to go to all this trouble though.