Canadian here. I think UK office because my family has lots of UK ties and grew up with that humour.
Eventually saw the US office and hated it.
Canadians are culturally stuck between US and Europe, so it can go either way
From the Netherlands: US Office, as growing up, that's the version we had on the Comedy Central TV channel.
From the Netherlands, UK Office, as that one was broadcast on Dutch television already before the American version existed. So I guess the answer depends on your age :)