That’s a federal court Dominique. They can subpeona anyone they wish. If you are a US citizen, a resident of the US or do business with US residents you are likely to be subject to legal action.
Setting up an offshore corporation slows the process, but it does NOT shield one from prosecution. If it did EVERY illegal enterprise would set one up and thumb their noses at Uncle Sam. Obviously the US government will not allow this to happen.
I am sure Jay Cohen set up an offshore corporation and if I remember correctly his Sportsbook was in Costa Rica. He was still treated to a stay in a federal prison.