Things do not change unless people learn.
What is a common thread among the destruction of street cars and the current state of mass transit in the USA?
Corruption.
Everything from the placement of rail and bus stations to the location of rights of way for mass transit is not governed by the best solutions to the problem, but by what is politically acceptable.
Any time people propose a major shift in any industry it is prudent for taxpayers to follow the money. We the taxpayers must make sure that the changes being paid for by the taxpayers are the right changes, not the most profitable for the well connected.
To use a blanket statement like "Since streetcars were mostly overrun by subsidies for automobiles and airplanes," is to throw out a polically popular punch line and ignore the bigger problem of corruption in our government at all levels.