I'm a US citizen, and worked for banks among other vile institutions, and have conducted myself politely when in other nations. It's common courtesy.
I've been incensed at others I've worked with who refused to extend common courtesies to other human beings simply because they didn't share US citizenship.
We're all human beings. Might as well face it -- US citizenship does NOT confer anything other than a US passport and the rights guaranteed therein. It doesn't make you on whit better than the other nationals with whom you work.
mh