We can still do a better job teaching metric to kids, without needing to tear down every building to replace all the 2-by-4s with "50x100s." But yeah, that means dealing with the fact we don't have everything following the standards and our pipe threads, screws, etc. will always be different to yours.
That’s true of everywhere in the world at the time they made the switch (give or take a decade). Why is that a problem unique to America?
You can make a better case that we were fools to not stay the course in the 1970s than a case that we should try it today. Even the 70s seem more like the very tail end of a window. 1776 would have been a great time to do it!
Why does the absolute number matter? Every trades truck/stockpile will need to stock double for some time, not some absolute value increase.
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?
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.
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.
[1] https://www.reddit.com/r/Metric/comments/hmyt6a/how_to_measu...