This is kind of pointless for the US without a national app. I worked in four different states last week no way I am going to look up if they have an app. There are still many road warriors out there I haven't had a non full flight since July even on a trip to the UK.
I think you and a lot of others don't understand how the system works (at least not the "Exposure Notifications Express" system which is new as of iOS 13.7 / Sept 1st).
You don't need an app in every place you go. The "app" needed (what it means for it to be "turned on" in a state) is to report COVID-positive status and trigger sending of notifications to those the COVID+ person interacted with. What you need in every place is your phone, with its BLE tech, keeping track of the other BLE IDs it sees.
If you enable exposure tracking and notification, and go to four different states, and interact in one of those with a person who was also visiting that state, then that person goes home, tests positive, and
the state where they tested positive has the "reporting" side enabled, you will get a notification that you have interacted with someone who tested positive.
Your state doesn't have to have enabled anything.
The state where you two met for drinks doesn't have to have anything enabled.
Only your phones had to have something enabled (permission to keep the list of BLE IDs seen in the past 2 weeks),
plus the health system where the positive test got reported.
It is that integration with health systems which takes time.
This isn't a wholesale replactment of traditional contact tracing, which would require that person to remember all the people they interacted with in their business trip, happen to have kept your business card or at least remember your name and where you had been visiting from. That all still goes on. This gives a second source for contact tracing which is reliable so long as the contacts in question had enabled contact tracking (locally on their phones). Both approaches have blind areas. But together, contact tracing, which is
critical if you actually want to return to a "normal" economy anytime soon, becomes much much more effective.