Have had 5 emergencies where I felt emergency services on the ground would be prudent while flying in the US in the last 2 decades. " Declaring an emergency, request fire and rescue upon arrival". Worked every single time. And I am sure "roll the trucks" would have worked too. Before that, I flew in the EU (for almost a decade, and not from the US myself) I declared an emergency, twice, did the "mayday-x3", repeated it on every frequency, advised ATC we would be unable to vacate the runway due to a hydraulic failure, and still had a couple of aircraft behind us forced into go around because ATC did not realize that we would need a tow after landing. Maybe the US isn't very ICAO, but at least the controllers understand English and aviation. (yes, I have had bad luck, and I have at least another 5 emergencies that didn't require "the trucks".)