Kuwait paid about $16B after the first Gulf War and continues to pay for US troops based there. It's unclear how much that is, but Japan (for example) pays $2B a year to keep US troops in Japan.
That's independent of things like international trade being executed in US dollars, which is why the US can control World trade: at some point everything needs US dollars. That's why US sanctions are so effective and why people who are very rich and powerful still hate being sanctioned.
Even outside that, paying for troops to stay was often known as tribute.
Edit: in any case I wouldn't actually argue that the US is an empire in the traditional sense. It has been the the unchallenged hegemon for nearly 30 years and before that the leader of half the world for another 40. I think speaking of the American Empire is a reasonable shorthand, even if it misses many subtleties.
That meets no definition of empire I've ever heard of, and I'm not sure what you are even arguing anymore. Are you just trying to find something to be right about?
Come on!
Look outside your idealogical bubble for a couple of minutes, and think about what your point is.
If your point is that the US isn't an empire, then sure - I think everyone will agree it was never the same as the Roman empire or the British Empire.
But the post cold-war US was something, which involved it obtaining a lot of power in many forms. Some of this power was financial and was based on the US dollar being the reserve currency, and even the US's enemies had little choice but to concede to that power.
When the OP said that this is the end of the US's empire, that is what they meant. Think about that - if you disagree, then fine. There are reasons to think they could be wrong (this has been tried before and didn't work then).
But claiming the US is not an empire because it didn't collect taxes (!) as though that somehow invalidates the argument is just wrong.
It's kind of like duck-typing I figure. If it looks like an empire and behaves like an empire it's probably an empire.
The four behavioral characteristics that clinch it for me are: [1] the continued unilateral interference in the sovereignty of other nations either covertly or overtly; [2] the non-participation in international norms; [3] the continued garrisoning of territories in other nations; [4] the historic and current role of the dollar and the US-backed financial systems and institutions globally.
[1] https://en.wikipedia.org/wiki/United_States_involvement_in_r...
[2] https://en.wikipedia.org/wiki/List_of_treaties_unsigned_or_u...
[3] https://en.wikipedia.org/wiki/List_of_United_States_military...
[4] https://en.wikipedia.org/wiki/Reserve_currency#United_States...
There is a non-trivial amount of oil traded in the euro, and also see [1], [2]
[1] https://en.wikipedia.org/wiki/Iranian_oil_bourse
[2] http://www.nytimes.com/2008/02/25/business/worldbusiness/25i...