I have mixed thoughts about this...not so sure there won’t be other nations suing the US after this...what’s to stop them? Even if there’s no grounds to do so doesn’t mean they won’t try.
That’s what Obama said as well.
Other nations already have that power within their own nations.
The way I see it, the argument is muddled by the ‘diplomatic immunity’ thing, meaning those against the right to sue Saudi conflate this with an attack on diplomatic immunity.
Terrorism is an act of war and Saudi is responsible for acts outside what would be diplomatic action, otherwise a belligerent in a war can come to the US and claim diplomatic immunity while shooting people and blowing up stuff..