It may be something as simple as that . . . the American "sense of humor" is often thought to be less ironic than Aussie/British/European humor. It might also be education levels or life experience (travel) . . . It has been my experience that those who do not travel much have a far different outlook on life than those who do.i am of european heritage and if anything i would connect more with americans than chinese. having said that i agree with me countryman legion that most countries and i include america don't get the aussie sense of humour.
Interesting question, actually.