Iran is a threat because they frequently disagree with the United States. If the world was a workplace, the US would be the boss, and Iran would be the contemptous insubordinate who refuses to follow instructions.
Anybody who thinks Iran is a military threat to the United States is, as The Comrade says, functionally retarded. The only way Iran can hurt the United States is cutting off access to oil, and the only way to do that is to have a Navy and Army capable of holding off the United States. Which is, of course, a completely ludicrous suggestion: in terms of conventional warfare, the United States military is capable of destroying just about any two or three countries in the world, simultaneously.
So, if your point was to prove somebody wrong by proving that Americans are retarded, consider yourself the victor.