NEW YORK — Americans are greedy, boorish warmongers. Or so say some unexpected sources.

While such sentiments wouldn't be shocking from some people in foreign countries, many of the folks saying so are Americans. In fact, they're among the people who enjoy more of America's blessings than anyone else: celebrities.

Although most stars were mum directly after the terrorist attacks, many seem to be piping up again -- often when they're on foreign soil, where it seems they feel safer to express their opinions.

Some celebs didn't even wait a month after Sept. 11 to launch their tirades. In the Sept. 23, 2001, edition of the Greek newspaper Eleftherotypia, Johnny Depp explained why he didn't vote by calling his homeland venal.

"America is a giant dollar machine, so if you really believe that they'll give the same rights to the baker or the plumber as to a guy who runs a huge multinational company, you must be really naïve," the Kentucky native said. "I believe that the American Dream is based on greed."

While celebs are often called on to help causes like breast cancer and AIDS awareness, stepping into the political arena is like navigating a minefield.

"We're used to sitting back and watching Arnold Schwarzenegger or Barbra Streisand or Tom Selleck as the Terminator or Magnum P.I. or singing 'People Who Need People,'" Syracuse University cultural historian Robert Thompson said. "But when we see them as spearheads of political philosophy, that's where we start to think, 'Shut up and sing your song.'"

In June 2002, the Daily Express in London reported Tom Cruise said the state of affairs in America was in shambles.

"I think the U.S. is terrifying and it saddens me," he said. He later stood by those comments but denied having said he'd like to raise his children in another country.

Now, with the potential war on Iraq dividing America into those who support military action and those who don't, the star-studded rhetoric has become deafening.

In the Oct. 17 London Guardian, Natural Born Killers star Woody Harrelson called the U.S. government corrupt and said that many Americans had lost their senses when it came to the war.

"Every media outlet is beating the war drum and even sensible people can hear nothing else. In the U.S., God forbid you should suggest the war is unjust. … In a country that lauds its freedom of speech, a word of dissent can cost you your job."

About that last line, at least, Thompson agreed, saying Politically Incorrect host Bill Maher's show was canned by ABC for making comments perceived to be anti-American. Others, however, have said the show was canceled because of sagging ratings.

"Especially after the Bill Maher incident, celebrities may feel they might not get the fertile ground here for their ideas that they have [in Europe]," Thompson said.

Author Norman Mailer also took a whack at Bush, suggesting to the Frankfurter Allgemeine Zeitung that the president should have been a ballet dancer because of the way he "wiggles through world politics."

In an e-mail to Foxnews.com, Mailer wrote that he spoke to a German newspaper because he felt the foreign press would be more open to his opinions than the domestic press.

"I am often ready to talk to foreign newspapers because it is the best and sometimes the only way to get the American press to pay attention to what I say," Mailer wrote.

"I was not trying to say George W. Bush is effeminate, but rather that he possesses more grace of body than of mind," he added.

But not all celebs are holding their tongues until they get to foreign soil.

Actor Sean Penn took off the gloves, taking out an ad in the Washington Post that told Bush not to attack Iraq and took him to task for his domestic policies.

"Your administration's deconstruction of civil liberties all contradict the very core of the patriotism you claim," Penn's ad said.

Harrelson and Penn did not return calls for comment.

But by making strong stands, celebrities don't always help their cause, and may hurt their own image, said public relations specialist Mike Paul. Their reputations as dilettantes can overshadow everything else they do in their professional or private lives, he said.

"They should expect a huge backlash," he said. "When Barbra Streisand says something, people who like her will say, 'She thinks just like me, rah-rah Barbra.' But others who aren't Barbra fans ... will think from the opposite perspective and say, 'It's just another liberal spouting stuff.'"

But though it's easy to brush off celebs as political dabblers, Thompson said it's important not to ignore any segment of the American community, especially when it comes to a decision as momentous as the Iraq invasion.

"We can't take these people for more than they are simply because they're celebrities, but on the other hand, we can't simply say that because they're stars, their opinions are therefore useless, meaningless and wrong," he said.