TAFAIK there's no MSP-ICN flight and DL has stopped serving NRT-ICN, so I don't know what your second routing means.

Have you looked at connecting through China (PVG, CAN, or PEK), possibly using CZ or MU for the flights to Vietnam? You need to find a connecting airport where you can arrive on DL early or a SkyTeam partner early in the day. The increased flights from SEA could be promising here. Check also whether there's a SEA-HKG nonstop on your travel dates that would connect with Vietnam Airlines.

Another idea is to look for SkyTeam partner flights that arrive early into Asia, such as the CZ LAX-CAN nonstop, MU from LAX, and KE from several gateways including ORD.

If you must do the overnight, try at least to take a later flight the next day. Anything less than 24 hours doesn't count as a stopover on international.

If you connect through Tokyo, look into connections through HND. [This would be easy with an overnight in central Tokyo, but if it's a connection on the same day, be sure to allow plenty of time to change airports.]