Yes, you could. We could even go so far as to threaten war.
The real question is will we? And that answer is no on both fronts. And because of that no payment is going to happen.
The court would eventually be compelled to do something to ensure restitution if there was an adverse judgment against SA as a result of this bill. That doesn't mean they'd immediately freeze $750b in Saudi-held treasuries, but the assets are not untouchable.