An additional bit of information:
The inability to see my home router is definitely a frequency issue. For some reason, higher channels are not seen in the scan results despite the countrycode being set to US and an updated regdb that (at least) gives sensible results from
iw phy phy0 info
Obviously it doesn't work with the old regdb either. I've seen reports that on some OSes (wasn't the case for my Ubuntu unit) you need to set the countrycode in Raspbian first for some strange reason.