The study found that PFASs were detectable at the minimum reporting levels required by the EPA in 194 out of 4,864 water supplies in 33 states across the United States.

So, about 4% of water supplies had something at the minimum reporting levels; which must be above the detection limits, but may not be at action levels. I'd probably be more worried about heavy metals and organics in some of those locations than fire-fighting foam, but I drink groundwater, not surface-based treatment plant water.