Sadly, they were largely decommissioned and replaced with buses or nothing.
We badly need to get more trains moving through American cities. I'd prefer grade separated, but honestly even if we had streetcars running in from all the suburbs that'd be pretty great.
It's also worth mentioning the General Motors Streetcar Conspiracy: https://en.m.wikipedia.org/wiki/General_Motors_streetcar_con...
There's pretty good incentive to see streetcars removed if you are a car company...