If there were several flights a day MSP->NRT i'd say go for it, but given that you're risking a 24 hour delay in MSP I'd try for an earlier flight.
If op missed his connection at MSP is there a chance DL would reroute to PVG via LAX/ SFO/JFK on China Eastern? or via CDG/AMS on AF/KLM? Or would that depend on medallion status? Is there a way to connect to the DTW->PVG flight if theres a missed connection at MSP?
All things to think about, but my vote is to schedule a 2-3 hour layover at MSP.