The discussion has gone into the threat of invasion. What else are you going to do if Mexico says "no, we are not paying?" You could stiff them out of money owed, but that would lead to the destruction of our credit/purchasing power.
If you are going to make a court analogy then who do you think will serve as the jury? It's gotta be the other nations of the world. If you can get them to go along with that, you MIGHT be able to get Mexico to bend over. But, I doubt they will because your position is batshit crazy and would be a clear attempt to impose our will on a weaker neighbor. They are not going to go along with it and we will either end up isolated, economically crippled and with our demand for payment unsatisfied or you take the next step and invade Mexico. That would possibly lead to a military response against us. You think we are big shit (we are) and we can do whatever we want (we can't).
Even the neighborhood bully is limited in how far he can push the littler kids around before they decide to join against him.