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.

In the UK the metric system is used in business, construction, science etc. Really anything serious. Imperial measures seem to persist informally for things that are difficult to visualise, like body weight or speed. Or things that are customary like a pint. I will ask for a pint because that is how much beer I want to drink. Not because I actually care what unit it is in. And young people haven't got a clue how to add up pounds and ounces or inches and feet.

Ireland is 100% metric, yet you go into the grocery store and the butter is in 454g blocks.