I tried it out (american, british, korean, italian, japanese) and couldn't really get any control. Sometimes the american siren would sound different, but asking for a siren of a specific country would just give the american sound. Maybe better prompting would help. I used "isolated american ambulance siren no traffic".

Thats an interesting q ;

What about the ring tone, busy tone, disconnected tone for any country over time. 2600 vibes (pun)