Re: Size.
"Honestly, I suspect the American problem might be the telcos, and their inability to play nicely with each other."
The 911 system came about when Ma Bell was a (near) monopoly, so that wasn't really an issue. It wasn't set up to be a national service, mostly because of the size of the place, but also because the usual suspects balked at the cost and started yelling about "State's Rights". So even though the 911 number was reserved nation-wide, and the switch gear knows to keep such calls local, not everybody got the system immediately. Each individual region had to pay for their own system, so the roll-out was slow with multiple generations of hardware in use. However, the various call centers do have communications capability between each other in places where it makes sense. Here in the Bay Area the emergency folks can co-ordinate (mostly) seemlessly. But it would make little sense to include the Sacramento area or the San Diego area or Los Angeles in that. With 440 (last time I checked) 911 call centers in California alone it would become unwieldy if each one had to talk to even 10 percent of the total.
So while it looks strange to folks coming from a physically much smaller country, it actually makes perfect sense here. And yes, once in a while there are edge cases where it would be handy if two (mostly) incommunicative call centers had better info sharing capability. We are getting there. Fortunately that kind of emergency is few and far between.
Things like wildfires are handled with their own communications systems, where the local folks in charge can communicate with crews coming in from all over the nation (and Canada, occasionally... and we send crews North to help them, too). Same for the Coastguard.