Eh, this is how the game is played. If they're smart, they'll push back against it, and then they and Biden will get to use it to fundraise on. If they're dumb enough to try torpedoing legislation that would otherwise pass... Well, that'd be one heck of a thing.
Which countries would be willing to do that? Smaller countries would have much more to lose by becoming enemies of the United States, and I don't think anybody, save an entirely hypothetical China/Russia/EU coalition, would be willing to invade or try launching sanctions. If anything,* they'd start throwing resources at helping the illegitimate administration maintain peace and stability.
*I should have specified - even this is a very big if. What's infinitely more likely is that they'll hunker down to see how things shake out and do little more than speak out against whatever's happening. And, of course, this is all an extreme hypothetical, so who even knows?