In 2004, after a Korean missionary was killed in Iraq, he sang lyrics from another band's song called Dear American, including the words "Kill those f---ing Yankees who have been torturing Iraqi captives" and "Kill them all slowly and painfully".
He's since apologised for any hurt caused, saying it was part of worldwide anti-war sentiment at the time.
Before that, the Gangnam Style singer smashed a model US tank at a protest the death of two South Korean teenagers who were struck by a US military vehicle.
The anti-American outbursts have surfaced at an interesting time, with Psy performing at a Christmas concert at the White House over the weekend.
The former chief prosecutor for the military commission at Guantanamo Bay says this is an example of Washington's double standards - welcoming criticism from the outside, but not from within.
But retired US Colonel Morris Davis concedes it would have been difficult to disinvite Psy from performing at the White House.
Interviewer: Liam Cochrane
Speaker: Morris Davis, retired US Colonel and law professor at Howard University
DAVIS: Well I think the whole thing came to light kind of late in the process. He'd already been announced as one of the performers and at least my understanding was, at least the first I'd heard of it was a few days before the event. And I think it really put the Obama administration in an awkward position of whether or not to attend the White House Christmas Gala or to remove Psy from the line-up or just to suck it up and press on, and they chose the latter. And it was interesting seeing the Commander in Chief shaking hands with someone that was singing "Kill the Americans", "Kill them slowly and painfully kill their families".
COCHRANE: And let's just explain why we've brought you into this conversation, can you remind us of your history with criticising the American authority and how that played out for you?
DAVIS: I was chief prosecutor for the military commissions at Guantanamo from 2005 to 2007, which was during the Bush administration. And I resigned in October of 2007 because I objected to using evidence that was obtained by torture, and also the political interference by the administration in the process, particularly the David Hicks case. When I did that the Republicans and President Bush was in the White House, it wasn't popular with the Republicans that I spoke up about torture. I retired from the military and I went to work for the government and President Obama came into office promising to close Guantanamo and end the military commissions. And when he began to back-peddle on that promise I wrote an op ed in the Wall Street Journal that said it was a mistake to try to have military commissions and trials in Federal Court, that it was a double standard, and I was terminated from my government job shortly thereafter for writing the op ed. So the no administration has been particularly fond of criticism.
COCHRANE: In that light though do you see this as hypocrisy to allow side the criticism but to now allow the criticism from within?
DAVIS: Yeah apparently it's better to be a rich born celebrity than it is to be a 25 year veteran of the military. As I said in a tweet over the weekend the President extended a hand to Psy and gave me the finger, so I think it is a bit hypocritical.
COCHRANE: How do you think the American public will react to Psy's comments?
DAVIS: Well I think veterans in particular are going to be upset because he's specifically said, kill American service members, kill their wives and their daughters and kill them slowly and painfully. I mean it's kind of hard to quibble about what those words mean, there's no misunderstanding about it. At the time he said it in 2004 I was one of those service members, so it's a bit personal when somebody's saying that you and your family are to die and die slowly and painfully. So hopefully his apology was heartfelt and he really meant it. But again it was ironic to have someone whose made that kind of comment, because other people, other foreigners have said, tried to incite people to kill Americans, instead of getting a handshake they get a Hellfire missile from a drone. So again it's a little strange for the administration to be smiling and shaking hands with Psy.
COCHRANE: We will wait and see what the American public's reaction is to the comments and to the White House performance. If I could return to the issue of Guantanamo Bay, as you mentioned President Obama did pledge to shut it down, I think it was within a year of the pledge that he made. That time has well and truly come and gone. Why is it so difficult for America to get rid of this very controversial facility?
DAVIS: Well I think President Obama was sincere when he took office in January of 2009, the second day in office he signed an order that said the prison would be closed within one year of that date, which as you mentioned came and went a long time ago. I think he sincerely meant that. And when he took office in January of '09 our economy was crashing, healthcare reform was his number one priority. And I think others like Dick Chaney and Liz Chaney and the far right went on the offensive and went on television and the print media, and sold the American public on the notion that you're either with us or you're with the terrorists. I just don't think the administration was willing to invest the political capital and to stand up and fulfil the promise. I just think it went on their top ten list there for a while, and the other side persuaded the public to back down. So I think here in America the vast majority of the American public really couldn't care less about Guantanamo and the people that are there.