[XorNot]

The scenario being unlikely doesn't make the OP's point irrelevant: the situation you see today is because that scenario doesn't happen, and it doesn't happen because countries are relatively circumspect about the way in which their military aid is deployed for exactly this reason.

[maxglute]

I'm not questioning relevancy, but escalatory logic. CONUS vulnerability is going to increase with mid/high end missile/drone proliferation. But skipping over proxy fight vs lesser adversaries with limited CONUS strike capabilities vs peer adversaries with significant CONUS strike capabilities is not particularly sound. Now it may get there if existential, but that's far from first run on escalation ladder.