It's possible to have multiple levels. Most places in California have both City and County levels of government. San Francisco is weird in that it is a combined

It's possible to have multiple levels. Most places in California have both City and County levels of government. San Francisco is weird in that it is a combined City and County. The logical outcome would seemingly be to have one metropolitan county covering the whole Bay Area with responsibility for transport and other shared concerns then have the various cities (which are effectively boroughs) underneath that. Who knows, maybe they could organise integrated fares across the patchwork of different transport systems!