The Washington Post thinks so:
For the past three decades, the United States has been Iran’s “Great Satan.” Schoolchildren learned to chant “Down With U.S.A.” Conservative clerics sermonized against America. Anti-American murals depicting images such as a skull-faced Statue of Liberty dotted Tehran.
But since Iran’s disputed presidential election last month, another Satan has gained ground: Great Britain.
As we reported earlier, before Rafsanjani’s speech, when the head of the organization that oversees the Friday prayers spoke, the audience refused to repeat the chants coming from behind the podium. When he said “Death to America,” the people responded with “Death to Russia” and “Death to China” instead. (Both countries have recognized Ahmadinejad.)
The Washington Post cites experts saying that the Iranian government, while intent on staying in power, may not be focusing on the U.S. as much because they do not want to unnecessarily poison the atmosphere before U.S.-Iran talks can begin.
niacINsight - The Blog of the National Iranian American Council (NIAC) 
The Post article is poorly put together. Key evidence provided to support the claim is circumstantial and the remaining supporting points are hearsay. The primary evidence is that the Iranian regime expelled two British diplomats, but it fails to mention that there are no American diplomats to be expelled in Iran. Next evidence is that the Iranian regime kicked out the BBC bureau chief, but it fails to mention that VOA has no official office or presence in Iran. Another primary evidence is the arrest of the British Embassy staff members with the charge of fomenting the unrest, and again it fails to mention since there is not American Embassy in Iran, there are no American Embassy staff members to be arrested or charged. The rest of the supporting evidence is hearsay.
During this past Friday’s prayer, the propaganda lead continued to shout Death to America and Death to Israel from the loudspeakers. It was the people who refused to go along and, instead, chanted Death to Russia and Death to China. This can hardly be evidence of a shift in regime’s policy of demonization and blame.