I don't think we as Americans insist on anything of the sort. It is just part of our heritage and where our country has come from. You mention your country has an aversion to such things, which country is that? Japan? If it is, we know why.
As far as bad manners is concerned we as Americans will always continue to say "I love my country" and "God bless America." It is not bad manners in the U.S. to say such things so why would any foreigner care if we did? Both in this country our theirs. (It has to do with respecting of others cultures and practices. These mere sayings can cause no harm. You are for respecting ones culture are you not?)
It sounds like you are a bit jealous that a group of people no matter what their backgrounds or differences are, can rally around the flag and country. America has proven this time and time again. You get squeamish over that? That is so odd.
I know you have an agenda, I have seen your posts. They are actually quite amusing!
God Bless America