I've travelled a bit and culturally we are not that different in the West (especially the English speaking countries) but I have noticed that humour IS noticably different, just like accents are. British, American, Australian and New Zealand all have different styles of humour that can take some getting used to.

I don't mean to sound snobby but the US exports a LOT of crappy sitcoms so perception of US humour where I am from at least is not great.