Well they are americans... I often find the polite but firm "excuse me" while guiding the other person out of the way works or instead of debating which side to go just walk in the middle :)) they soon move outta the way ;-)
Do you have something really interesting/different/odd/something that's not commonly known about you you are willing to share? I'm allergic to photocopier ink... suffering red hands and a bad case of the sneezes as I type?!! :-(