To be clear, if it were in OP's interests, he could purchase this routing on these carriers on a single ticket and not encounter any issues. Depending on whether the origination and termiantion "USA" are the same, this will be viewed as either a round-trip to HAN or an open jaw.

All of this presumes that by "USA" OP does not mean LAX on the outbound and GUM on the return.

Would be most helpful if OP would provide the "USA" locations for 100% certainty.