[ds9]

As a USian I can testify that there's a lot of irrational opposition here. Disclaimer: I don't have scientific sources on this, just subjective impressions from a lot of little interactions and clues.

The resistance seems to be largely: (a) older people who doubt their own ability to adjust (b) right-wingers who are convinced it's a socialist conspiracy or somesuch (these are people who think international cooperation is taking sovereignty from the US, or something like that - they're a bit incoherent) and (c) politicians perceive it as unpopular and risky to advocate (presumably because of a and b) or just not a vote-getter.

I've occasionally tried to promote SI by using units in casual contexts, but it's perceived as pretentious or obnoxious. The situation is better online as I participate only in fora like this where US obtuseness is not necessarily expected. It is hard to even find products like thermometers and measuring cups (for cooking) with all-SI.

[marcosdumay]

We don't use measuring products that are all SI outside of the US either. You are big enough that it's worth making a dual use product.