I am also not a typical American. I am over 195cm tall and have a big bushy, curly beard. I feel this is relevant as I can sometimes come across as a sort of intimidating person due to sheer size. I do usually have a goofy or aloof expression though to slightly offset this. In no way do I walk around with a mean or angry expression.
If you could understand Japanese cultural behavior and try to adjust to such behavior, that would be great. Maybe reading a book about the topic help you.
Other than that, just smile! It is true that not many Japanese are used to see 195cm tall person, but as long as you act friendly, it would be okay :)