JAL looks like they have pretty cheap fares from ORD-NRT and NRT-GUM. (A 747 to Guam? Since that is an international airline, does that mean that I would have to book separate tickets (ORD-NRT + NRT-GUM)? Would the transfer in NRT workout with that?

What exactly are the rules for foreign carriers serving US destinations? Would ORD-NRT-GUM be ok because there is a stop in NRT, and thus it is really two international flights together?

ANA seems to allow you to book ORD-KIX-GUM - but here the ORD-KIX leg is on United. Oh to understand the bizarre regulations of air travel...