I think you'll find that's already the case. MC/VISA would have an implicit underwriting by the US govt should they ever be in extreme strife. We've already seen this happen before, the UK govt bailed out RBS, largely because of things like being responsible for 1/3 of all transactions that happened in Europe at the time.
Various airlines were also bailed out over the COVID period. So I'd say that it already exists, except the public sees no benefit.