Runners should be able to wear whatever they want.
What in the hell does the USA (or any other national government) have to do with running?
Do they fund athletics? Not unless you're in the US Army program like Robert Cheseret. Every major running shoe company gives more money to athletics professionals than the federal government. Even USATF isn't funded mainly by the federal government.
So, who is responsible for athletic performance? Athletes, their coaches, and their sponsors.
To illustrate this point, let's look at Team USA posterboy Dathan Ritzenhein. If he runs a great race, it reflects on him, Alberto Salazar, Nike (in that order) and various other important people in his life. It has precious little to do with the USA. You didn't make him run fast. I didn't make him run fast. And nor did our tax dollars.
By the same metric, few would credit Eritria with the success of Zersenay Tadese despite the fact that it is entirely possible that he received proportionately more support from his government relative to USA athletes.
But I digress.
Unless we start talking about soviet-era dopers (and underage chinese gymnasts for that matter), national governments have had very little control and influence on athletes.
Therefore, instead of viewing the USA singlet as a privilege, we should see it as an encumbrance for athletes and their sponsors who should be appreciated enough for who they are to be allowed to choose what they want to wear.