There probably already is

250,000 gallons (if it was 10 cars and all 10 converted perfectly to HCl, and all of it went into the water supply) into a water table of, lets be conservative with 10 billion gallons, is 0.00002% concentration or .02ppm

Compare this to your stomach, which has an hydrochloric acid concentration of 5000ppm.

So yes, I would have no issue with it. All the water you drink mixes with a much higher concentration of HCl every time you drink it.

Like I said, their is a hysteria building around this and a total lack of nuance and understanding.