Exactly: the entire world has a standard, and the US is doing its own weird thing.
The long-term gain is being able to sell your stuff to the rest of the world, and being able to import stuff from the rest of the world without paying a Weird Format Tax.
Would you rather manufacture stuff for 8 billion people, or for 340 million?
You could also argue that North America should convert to 50hz 220VAC for electric services, so that one line of products could be sold to the entire world. But the switching costs would be huge and manufacturers generally have no problem making the few changes that are needed to make products for export, or when possible designing their products to accept either standard.
Cutting metric or imperial threads in a pipe fitting is a programming code change in a CNC machine, and maybe using a different cutting tool. Easily done for an order that's going to be exported.
So I don't think manufacturing is a big concern, and not the reason we've stayed with old standards in many cases.
k what's your quote on replacing every screw and bolt in America (and of course tapping new metric threads for those screws and bolts to go into). Also replace every pipe in every house.
There would need to be like a minimum 50-year transition where everything will be worse (keep both of everything in stock because both old and new need maintenance) and we'll probably have more confusion and mistakes over what units were being used during that half-century.
I love metric. I think it's awesome. But I'm not sure what anyone expects anymore. We attempted the same half-assed conversion Canada did in the 1970s when Jimmy Carter was President and people were pretty sane. We did only a little bit worse than they did[1] though. It boggles the mind to imagine a US populace as determinedly political and polarized as they are now adopting even a slightly inconvenient lifestyle change just because the government said so. Therefore, "you guys should just adopt metric" seems less than productive.
The long-term gain is being able to sell your stuff to the rest of the world, and being able to import stuff from the rest of the world without paying a Weird Format Tax.
Would you rather manufacture stuff for 8 billion people, or for 340 million?