Yes nearly every country is in some sort of hybrid state. In Europe you have the UK with one foot in the empire, but other countries also mix in e.g inches for tv’s, car wheel sizes and so on. It’s almost not a measurement, it’s more like a size scale (you don’t measure your wheels in absolute terms but you know what 19” rims look like compared to 17”). Ironically we put mm sized tyres on these rims.

I think the US should try to switch one area at a time. Just like we will eventually measure Tv’s in metric (Australia does already I believe) the US could probably ease into metric by adding more and more areas that use it.