What's crazy is that it's not consistent by language. Obviously we have British/Aussie/Kiwi vs US/Canadian English, but the Spanish speaking world is also fractured.
And not even by otherwise closely related geographical regions. The Nordics, one of the world's most internally cooperative group of countries, have Sweden and Denmark using the English British system, and Finland and Norway using the British American system.
Well that one you would kinda expect, as each Antarctic base is built by a different country - and complicated by some of the buildings being on stilts.
I've lived in Québec all my life, been in Montréal for 17 years, and I've never seen a building that uses the European style of floor numbering. It throws me off when I go in Europe. You may have experienced the exception rather than the rule.
We usually have RC (rez-de-chaussée/road level), 2, 3, 4...