my bad, it was during a parade, not opening ceremony

A parade during the Olympics or the entry of athletes on parade during the opening ceremony?
Either way l do not remember that happening, but it could have been Mexico City since they do not like us very much.
l can not imagine any other host doing that.

are you thinking of the 2004 Summer Olympics opening ceremony?

Due to the perceived unpopularity of the American-led
invasion of Iraq among Greeks, it had been expected that audience members would protest the war during the entrance of the American delegation into the stadium by booing; however, the roar of cheers and applause the Americans received was among the loudest of the evening.