> But, I don't see any US president standing for it before the election, or at least attempting to sell it to his electorate/funders, unless pretty much a hot war is happening.

I don't think it would be a hard to sell the American public on some kind of rationing if Beijing suddenly embargoes the US in a way that necessitated it. Given the economic dependencies that you cite, I think a US-initiated decoupling would likely proceed slowly enough to not cause critical disruption, just higher prices.