Good question. I don't know if there is an all-encompassing definition, but I believe people who do nothing (or spend the majority of their time) accusing the government of misconduct, condemning our military, and refuse to acknowledge all of the good our country and military do are "anti-American."
I have to disagree.
Although I think people who just complains and have no alternatives are irritating, I don't see that as being Anti-American.
IMHO, being Anti-American is simply put to wish bad things on USA.
Both Edwards and Giuliani are very Pro-American IMO, they represent the American Dream, the American Man.
I have no doubts that both guys, despite their differences in political opinion, love their country.
I would say the same thing about Cindy Sherman too, to make a really extreme example. She may hate certain structures of the government, but I have no doubts that she loves her country.
One thing that most of us non-Americans usually notices about Americans, is how patriotic they are, and how uncomplicated and true that patriotism seems to be rooted.
Let me put it this way: I've yet to encounter an American who's doesn't love his/her country.
It's one of the finest qualities that USA offers.
-Hedge