In Switzerland there is an app called Alertswiss which gets published by the government. They use it for critical alerts and you can also use it to see open warnings and where in the country there might be stuff happening.
If you think you'll be able to get Americans, ho already do not trust the government, to download an app on their phones made by the government, well I have a bridge to sell you.
It's amazing how these very unregulated tech companies that have been proven time and time again to steal user data and mess up have this blind trust from the public.
Also, have you seen any of the official government websites? They're buttgarbage. Go renew an amateur radio license online and tell me if anyone would intentionally install software designed like that on their devices.
Californian civil servants who do software engineering work are profoundly lazy and incompetent. I know because I walked away from two different pensions doing this because of my coworkers.