"Donald Trump rocked Europe so hard," the "Daily Show" comedian quipped.
National security adviser Jake Sullivan acknowledged the president's gaffe hours later but not before it drew scrutiny from some viewers.
Biden, who is in the U.K. for the Group of Seven leaders summit, is the 13th American president to meet the monarch.
White House official said Biden wants G-7 leaders to speak in a single voice against forced labor practices targeting Uyghur Muslims and other ethnic minorities.
A solar eclipse, the G-7 summit and a U.S. border crossing round out this week's most stunning images.
The announcement comes hours after President Joe Biden committed to donating 500 million COVID-19 shots to help speed the global pandemic's end.
It's like introducing America's new fiancé to its friends after breaking up with a bad ex, Kimmel joked.
The U.S. will share millions of COVID-19 vaccines to lower-income countries struggling with a shortage of shots.
Biden has an ambitious to-do list for his eight-day trip, which will end with a summit with Russian President Vladimir Putin.
The president said he plans to invite Russia, Australia, South Korea and India to an upcoming meeting of the Group of 7 nations, which he's postponed to the fall.