It's becoming clear now, especially in the summer heat/UV, that as long as there is too much COVID for effective contact tracing in at least one state and all states aren't in pandemic lock-down mode, the virus will keep moving around the country, state-to-state. It's a kind of COVID state-to-state tag or state-to-state jumping. Even if we social distance, wear masks, and wash hands regularly in some states, it's probably not enough if we allow travelers from states where too many people don't do this. Especially if the states with COVID under control are at least partially open for business such as indoor restaurants and bars. Plus, if some states don't effectively contact trace, then indoor activities need to remain closed in those states, or their numbers will eventually increase again even without travel from hot spots.
Since all states haven't followed safe reopening practices, it seems like a good idea where neighboring states join together who have, especially when they are in the same lock-down status/rules and with acceptable infection rates. However, all these partnering states would need to impose hard-line travel restrictions to/from lax states to stop recurrence in their states. Not just voluntary quarantine like we see, but hard-line forced quarantines.
Are hard-line travel restrictions between states possible in the U.S.? Probably not, unless they are forced on us by hospitalization rates that are too high to manage. Let's hope this pandemic doesn't get to that point, and we can lock-down effectively enough to manage this state by state COVID jumping or COVID tag. In the meantime, hopefully we can (continue to?) improve COVID patient survival/care and find better ways to keep our health-care and other front-line workers safe. Unfortunately, with the decisions we have made as a nation, whether or not consciously, it seems that our state-by-state COVID jump/tag will continue until we have herd immunity, hopefully through effective vaccination and not community spread.