Originally Posted by MatthewLAX

I'm not so sure NH would veto this.

But what may make this easier if OP books MEX-NRT-ICN/ULN/IST (somewhere you could go with just a negative test) on one ticket and then NRT-EWR on the other. That is still a valid transit in NRT (unlike USA - Japan - USA) and so what if "plans change"?