Delta are the only US major who so far have not retired the 757. As such UA and AA will be significantly reducing routes to non hub / primary airports one would imagine. AA are also retiring the 767 and A330. Until both start getting A321XLRs in 2023, things could be tough. UA have pulled EWR-SNN, SFO and EWR to DUB appear to be continuing on the 787, they ran ORD and IAD to DUB on the 757, haven't read what is likely to happen there so far, but their 767s are very premium heavy and are pretty much set up for LHR and other premium hubs, so probably not suitable for the likes of DUB/SNN/MAN/EDI/GLA. With business travel likely in the doldrums for quite a while, who knows whether that fleet will survive.
AA are taking delivery of several 787-8s right now, but I'd be wary of making any assumptions about them, rumours are rife that they'll be into chapter 11 once the CARES act expires on 1st October.
Very tough times ahead. The recession/depression resulting from the virus hasn't really bitten yet because everything is effectively in stasis due lockdowns.