They're actually both. Pretty rare but LA and SF exist as both city and county level entities.
In Sweden, we also have administrative regions translated as counties, which are lead by someone I'd directly translate as "county chief" (as in "chief over this tribe") but they're anonymous bureaucrats a normal person wouldn't know about. (The common translation is the less exciting "governor".)
For some reason, the UK doesn't issue the title of "count", only "viscount". "Marquis" is linked etymologically to "marches", an old type of land allocation boundaries, but again not in practice.
Also, in California: San Luis Obispo, Riverside, Sacramento, Fresno, Santa Barbara.