Well like few systems, such Portland, Seattle or Milwaukee could turn out to be ok once they are given some time. This class of modern light rail vehicle is really kind of new to the America; previosly early 2nd gen light rails were there heavily separate half trains like can be see n in Salt Lake City, Dallas or San Diego.
In places like Tacoma, Tempe, Cincinnati or Memphis Paso I cannot see what is the planned end game there, unless it's like as said, they get "paved over once the LRVs become life expired."
DC used to look like as it had potential and solid plan in place, but it turned out an exercise of the most pathological way of running an American urban development project.
In long time ago I saw a picture of possible Dallas streetcar expansion to South-Eest, where it could have formed it's own kind of Boston green line regionally limited system, but since I can't find a peep about it anymore, supposedly it was too grandiose for the time being :(
All in all you Americans would desperately need to see one of these 2nd generation modern streetcars frowing up from the "dowmtown circulator" forming its own independent system that offers additional high frequency service at the core regions of thelarger transportation network. Like Portland Streetcar getting Lake Oswego line or a few East-West lines running. Sadly, nothing like that there or elsewhere in the immediate future, it seems.
Anyway, this is my outsider view of things.