I think this would, in general, be a really bad idea. Kowtowing to nuclear threats would lead to a huge incentive for various countries to acquire nukes (both to make nuclear threats, and to defend against nuclear threats), and thus would increase proliferation (and nuclear risk) considerably. Of course, if you can figure out a way to get Russia to de-escalate, that would be great, though I doubt anyone here has any ability to influence that. Barring that, my sense is the best strategy for the US right now is to continue to provide Ukraine with much assistance without engaging Russia directly.
I think this would, in general, be a really bad idea. Kowtowing to nuclear threats would lead to a huge incentive for various countries to acquire nukes (both to make nuclear threats, and to defend against nuclear threats), and thus would increase proliferation (and nuclear risk) considerably. Of course, if you can figure out a way to get Russia to de-escalate, that would be great, though I doubt anyone here has any ability to influence that. Barring that, my sense is the best strategy for the US right now is to continue to provide Ukraine with much assistance without engaging Russia directly.