If the DAO is very explicit about non-US residents, they should also be able to show that in court, and it could be determined that the US citizens who ignored that waived any protections the court would otherwise offer. Alternatively, it might instead be that the DAO should have done more to ~spy on~ "know" their customers so they could determine that they're not serving US citizens.

The US could still argue that there's a US nexus in that the tokens are converted to US dollars