My Life as an "American Imposter"

I went to Oberwesel this weekend to see Rhein in Flammen, which was amazing and I will soon post an update describing it.  However I felt more inclined to discuss the masses of people (Ok well... 6 or 7 people...) who seem to think I'm a good person to ask for directions.  While I suppose I am legally a Kölnerin, I am certainly one of the last Kölner you would want to talk to about this stuff.
Maybe I just always really look where I'm going.
Maybe it's because I don't have a skateboard and seem unlikely to carry spray paint.
Maybe I just look really friendly and approachable.
Whatever it is, it happens.  Normally the questions are simple and easy to answer.  ("How do I get to the Hauptbahnhof from here?"  "Does Linien 12 go to Friesenplatz?" "Can you help me buy a ticket to the airport?" etc.) but on 2 occasions, people have stopped me on the street asking for directions to random restaurants that I have never heard of.  I remember one lady immediately knew what kind of mistake she had made the minute she heard my accent.
However, yesterday I was waiting for my Ubahn dressed in my jeans and an Iowa Football t-shirt, when suddenly a woman started speaking in terribly fast German to me.  I could gather that she wanted to buy a ticket for the Ubahn, but that the machine was giving her some form of trouble.  I was standing completely in shock unsure what to say.  I ended up telling her that I was learning German and that I could help her with the ticket machine, but she would need to speak a little more clearly.  (It turned out that the machine was totally broken).  That evening I was baking a cake with my host mom and asked her why Germans would want to approach someone in clearly American clothes for directions.  She said Germans probably think I just really like America and picked up my Iowa Football shirt in a random H&M or something.  It made me laugh that I've been wandering around Germany with Germans thinking I'm some sort of American weeaboo or imposter or something.  Perhaps I need to carry a sign.

EDIT: I talked with some other Americans in the program, and apparently H&M here really does sell fake American football t-shirts.  You can walk in the store and buy some shirt that says NORTHEASTERN MINNESOTA UNIVERSITY FOOTBALL or something.  So Germans probably really can't tell that my Iowa Football t-shirt was actually purchased in Iowa City.