I expect it to put additional pressure on the current stalemate over LPF and fish. In a no deal outcome then the WA and NI protocols still apply. If we start backtracking on those signed commitments, and put Dublin in a difficult position on the land border, that is where it will get difficult for the UK. Alienating our closest neighbours and what we like to think of as our ‘greatest ally’ against a backdrop of a pandemic is not the place we want to be.
The other factor is that the UK is not of greater or lesser importance to the US than Germany or France. The US under Biden will want good relations with all these countries and see the EU as an important part of that relationship. Biden regards Brexit as a mistake, but a Brexit that does not disrupt the EU or Dublin or cause any waves is not going to be a problem. In short, Brexit if you must, it’s your funeral after all, just behave yourselves while you do it.