When I was in Frankfurt in the 80s, it looked like every airport and train policeman carried a submachine gun.
In both Germany and the UK, I saw ordinary police carrying submachine guns outside the airport. (The UK surprised me.) Again, the 80s.
Has that changed? (I saw a couple of Italian police outside of airports with submachine guns post-2005.)
I've never seen more than a couple of automatic weapons in a US airport (and I spend way too much time in them). (BTW - M-16s aren't "big scary".)
I've seen maybe 10 US police outside of airports with automatic weapons in the last 30 years.
I was surprised how well armed the Indonesian airport police were in 2010.