1. The Wire Act makes it a federal offense to place or accept a wager over the telephone lines (including the internet) if the type of wager made is illegal in either the bettor's or the house's jurisdiction. There was a famous case where an American moved to some Caribbean island to set up an online book that took wagers from Americans. He returned to the US and got nabbed and spent a couple of years in the joint. All his activities were based outside the US and he even lived outside the US while running the book, but taking bets from Americans is enough. Actually, technically, taking bets from any person in any place where online gambling is illegal would have been enough. If he had taken bets from a North Korean (assuming online gambling is illegal there), he could have been prosecuted in the US just for that.
2. Any person who who is an owner or employee or knowingly provides material assistance, including advertising, software, hosting, recruiting customers, etc. for a gambling operation that violates the Wire Act is a conspirator and can be prosecuted under the Wire Act.
3. The UIGEA makes it illegal for any person in the US or any person acting on behalf of Americans to perform financial transaction services on behalf of anyone engaged in online gambling.
4. As with the Wire Act, any person who recruits another person or company to provide financial transaction services on behalf of an online gambling operation is a conspirator and can be prosecuted as such. It doesn't matter if the people ultimately providing the services (in this case, SWC and the bitcoin exchanges) are located in the US or not.