Simplified: you can make something illegal locally, but federal law will almost always win out.
The local governments are in compliance with state law until the feds use it for immigration enforcement. Then the supremacy clause takes over and more or less nullifies it. As long as it isn’t the local agency using it for enforcement, then they are in the clear.
I think that Flock contracts are getting cancelled due to unpopularity, not because of compliance worries. Can you point to any actual cases where enforcement of the state law led to a termination of service?
Probably not. A state can regulate how its own resources are used. It can't block a federal warrant.
Exactly. If they all submit to federal warrants, and the state has a law effectively against that, then it becomes illegal to use the cameras.