The problem is, it can actually be very difficult to evaluate the contribution of the courts and the military to the stabilization of international trade. A resident of Monaco could certainly stump me by asking "well, if the US or French military is so essential for my protection, then who is it who would be attacking me?"
I suppose I could try to come up with an answer (probably easier during the cold war), but the unsatisfying response is "who knows, but a rueful glance through history suggests it would probably be someone."
You probably believe that the rich need the US and allied military to the extend to which you agree with that answer. Same kind of goes for the courts - rather than point to a particular need fulfilled, a lot of people would say that without a system for resolving crimes, torts and even contracts, a modern economy simply couldn't exist.
"The American wealthy benefit greatly from the country’s legal system and business transparency, not to mention its armed forces."
I guess you'd agree or disagree to the extent that you believe the US military, government, and courts are required to maintain a safe, stable world where trade can take place unabated enough to allow the rise of a global elite. It's not just the US, of course - you could also ask if the haven of Monaco could survive without the military strength of nearby european powers.