I don't agree. This is pretty much the opposite of what I had to say earlier. And that's all I have to say. You can read through the comments to see the varying opinions, and in the end, Justine herself chimes in, and I still don't agree. This is all I have to say on this matter, because I don't want to get sucked in on something that I'm probably going to be accused of having no authority on, because I'm young, because don't brush against the publishing industry much - all of which are valid points.
Preemptively speaking, I know I'm going to get accused of being an idiotic, un-worldly American (and sometimes I deserve this epithet, when I am severely crippled about knowing non-Western cultures, and sometimes it is simply unfounded America-hate), but I will say this anyway. I don't ever have a problem, vocally or in my head, when someone from another country writes about Americans, for the fear of "getting us wrong." Perhaps it is because the U.S. is a very diverse place, and heck, who am I to have the authority to know whether one portrayal is right or wrong? The point is, there is no way to pigeonhole "the American lifestyle," because I'm fairly sure my life does not vaguely resemble someone who lives in Florida, or Mississippi, or New Jersey, or Oregon.
Therefore, I would assume it is difficult to say that someone is "writing Australians wrong" unless Australia is a shockingly homogenous place, which I doubt it is.
Just to clarify, I am aware everyone is entitled to have their own opinion, and J.S. Mill did say that in a free, uncensored society, it is impossible not to be offended by anyone. I guess the question is, drawing the line where offense because intolerable (ie racism) or when offense is simply over-PC-ness.
(Also, post-script: you rock, US hockey! Sorry, Canadians who are reading. Gotta support my homeboys. :D)