Lily Allen
Simon Seed/WireImage
The outburst came in the wake of the British singer's American working visa being unexpectedly revoked earlier this month, following concerns about her March arrest in London after she allegedly punched a photographer.
Introducing her song "Everything Is Wonderful" on Saturday, Allen, 22, described President Bush in profane anatomical terms and added, "I've been banned from America. That's nice. Oh well, that means I can't go back there. Good," reports MTV News in the U.K.
Friday it was announced that Allen had to postpone her September concert dates in America – and miss out on this month's MTV Video Awards – because of her visa woes.
"I am so disappointed that I won't be able to come to the States at this time," Allen said in a statement. "I want my fans to know that I'll be back as soon as I possibly can!"
Despite this weekend's onstage outburst, Allen – who was performing alongside such acts as Snow Patrol and The Foo Fighters – appeared upbeat during her 45-minute set, despite being "a little drunk" during the performance, she admitted, according to reports.
The gig was her first performance since canceling four European shows this month due to ill health.
