That it's a cultural phenomenon in the US and not in [other place x] does not make it immediately fake, and that some people may be faking it (I'll assume this

That it's a cultural phenomenon in the US and not in [other place x] does not make it immediately fake, and that some people may be faking it (I'll assume this is the case for argument) does not mean the phenomenon itself is fake. I'm an American that smiles and greets strangers regularly. It's not fake when I do it, and I know it's not fake when many of my acquaintances do it. I do know that this is not a natural/universal thing (though it took a trip to Japan for me to materially understand that). But just because it's not universal doesn't mean that, where it happens, it's backed by some kind of underhanded, guarded cynicism. So have a nice day. ;)