Ya know, it's a good point that not every gesture is made as an official statement of doctrine. Ever been to a baseball game against the Blue Jays or the Expos? Did you stand for their national anthem? Did you consider that you were pledging allegiance to a foreign power? Did you intend by doing that to turn your back on the founding fathers, and the government they created? Did you intend to renounce your citizenship and instead become a Canadian?
I'm guessing your answers to the last five questions were all "no." Yet saluting a flag IS a sign of allegiance. signaling allegiance to a foreign power is considered an act of renouncing citizenship.
No, many Americans instinctively stand out of RESPECT for the Canadians they are among. Although the Canadians stand to demonstrate their allegiance, no such allegiance is meant by the American fans.
Of course, the difference is that I don't believe Islam is worthy of any respect whatsoever (unlike Canadians, who do deserve a bit of respect!). It's a false religion that is essentially an insane death cult based on a Middle Eastern lunatic's syncretist version of the Arian heresy.
However, as I noted, the Pope obviously was a subscriber to the "sentimental ecumenism" philosophy. And in addition, I suppose he didn't want to risk offending his hosts.