Australians are not isolated. Where did that come from?
As for Europeans, they travel to America, Australia, Asia and South America very often. One of the most popular destinations for Britons, amongst others is Thailand.
I reside in UK, but this year so far, I have been in Amsterdam, Athens, Zürich, Belgrade and now I'm in Montreal in Canada.
Last year I was in Rome, Paris, Prague, Istanbul (but only briefly), and year before then Ann Arbor, MI, USA, Barcelona and Lisbon.
And I don't travel THAT much, compared to my best friend who has spent time in Cairo, Santiago and Nicosia last year. 3 Continents in a year. And for her this is usual behavior, as is for number of Europeans.
This kind of travel is rather usual for Europeans, and Australians. (as well as other)
I don't know where you got the idea that Australians are isolated.
Americans are not isolated, and that is certainly not an excuse for majority of Americans not actually seeing world other than America.