I see that you are still confused about how NATO works. While there is, indeed, some money that goes to keep the lights on at NATO headquarters in Brussels, Mons, and elsewhere, and there are a few key NATO military units (early warning planes, some drones, a few other bits and pieces), the burden-sharing problem is not about that.
In your meeting with Chancellor Merkel, you said:
I reiterated to Chancellor Merkel my strong support for NATO, as well as the need for our NATO allies to pay their fair share for the cost of defense. Many nations owe vast sums of money from past years and it is very unfair to the United States. These nations must pay what they owe.No, that is not how it works. The burden-sharing problem that has been the subject of many NATO meetings, including the Wales Summit, is about each country paying enough (the 2% of GDP aspiration) for their own defense. It is not about Germany or France or Estonia giving money to Brussels or to the US, but about Germany spending enough on new tanks, planes, ships and enough on a large enough armed forces and enough on fuel and all the rest. The idea is not that the US is getting ripped off, that somehow countries owe the US money, but that the alliance would be better off if all the allies spent more on their militaries. The past shortfalls do not mean that countries are in debt to the US or to NATO--it just means that their militaries are not in as good shape as we would like. It means that they don't have as many tanks or planes or whatever or that their personnel are not as well trained. The underspending over the years is problematic, but these countries do not owe any debts from the past to catch up in their accounts at NATO HQ. Again, this is not how it works.
So, next time you complain about burden-sharing, don't suggest that the US is owed money. Because it is simply wrong.