Willfull infringement is already a tort; the damages are set by statute at $150,000 (if properly registered etc). You do not need to add any provision to the G

Willfull infringement is already a tort; the damages are set by statute at $150,000 (if properly registered etc). You do not need to add any provision to the GPL to go after US violators. To the extent that doesn't happen means that copyright holders (developers) don't do it. Either because they don't know how, they didn't register in a timely fashion, they don't want to bother, or they don't want money.