I'm American so I don't really know, do Europeans generally ignore how AM/PM works?
IIRC the Romans created the system, so I'd find it really weird if it had dissapeared from common usage around there.
Also, every single picture I've found of a clock tower from Europe seems to follow a 12-hour convention.
Not in Britain we don't. Analog clocks were abolished by Henry VIII. Since then we kept time using sundials until digital watches were invented in the 1970's and Roger Moore wore one playing James Bond in 'The Spy Who Loved Me'.
Anyway that is not really the problem, we just learn from being kids that 12 is only valid for noon otherwise it is implicitely 0 as the next one is 1 anyway. And, at least in my country, we rarely say 12 as we use our words to say midnight/noon.