可以说， “你的态度很像一名美国游客。”

You are so "full of yourself." You are so "far up your own backside that your eyes are brown." Hey, do you think you're Jesus Christ come down for a walk?

You're way too conceited. You're already a legend in your own mind. You've really got an inflated sense of yourself. It's a tight squeeze in this room with you, me and your ego in it. You've got an ego the size of Hong Kong. How is God's gift to mankind this morning?

You could say your friend is smug or haughty. These are both adjectives that are very commonly used. (By the way, overweening is a very unusual word -- I had to look it up.) Some of the other suggestions are funny but also very idiomatic and people might just be puzzled when you say them.