however, America has more options than what you listed. :))
We can wipe out the islands without 登岛, and for short time 封锁, it doesn't have to get 南海其他国家的绝对支持.
It's not about what America is capable of, it's about America's determination.
Look through Trump's record, I haven't seen him took a tougher stand against PRC without back down. Even for a signed bill, he'd delayed execution or no execution.