[vlovich123]

Nope. Just a single pair of keys for one country. Make signing the message the responsibility of the country’s government. If city x needs to generate an alert, it sends the message over secure channels to state Y with the keys internal to them. State Y sends it up to the federal level. Federal signs it. Can even do it with a wrapped chain of trust. Then all you need is to validate 1 key per country with the rest acting like a chain of trust. Think domain names but for governments.

It’s a legitimate issue if the different levels of government are disfunctional / fighting with each other, but it’s better at that point to leave it as a political problem for them to solve.

[seszett]

That's a very simplistic take, and it's not going to work in many places. Like Belgium, I'm pretty sure the various sublevels would just setup their own channels and ignore the federal one.

Belgium isn't going to become unitary again because of a telecommunications standard.

Or French Polynesia, New Caledonia, in case of emergency they're going to send a message to mainland France to sign it and back? That's very impractical and better hope the emergency doesn't involve a problem with long-distance communications.

[SoftTalker]

States don't trust the federal government, generally. That's pretty much a founding principle of the country.