Which would be a real test of this court to see if the Constitution really has any validity. The issue will likely end up on the somewhat annoying fact that the Constitution specifies that there are three, not one, sources of supreme authority of the law in the US, the Constitution, Treaties and laws passed by Congress.
The laws allow actions that were not allowed in the past. It was not illegal to sue sovereign nations, it was simply not possible, there was no process or procedure to do that. The new law created a process to sue sovereign nations.
Like I said, this could finally be the solution to the US's traditional lack of providing foreign aid.
The solution though is really simple, the Congress need only add an "I'm rubber, you're glue; whatever you say bounces off me and sticks to you" clause to the bill.