I consider myself a very patiriotic individual for starters. I don't believe it makes you anymore un-American based upon who you choose in this fight. Ironman (tony stark) is a sybmol of American injinuity at its best, Captain America (steve rogers) is the symbol of dedication, honor, and duty. They both have gumption, they are both commited to the greater good, they just don't agree.
Now with this in mind, street fight, no armor, no shield, Cap wins 99.9% of the fights. Full armor vs cap with shield, you would have to be loony toons to think that a man with a shield can win against somebody that has inpenitrable, flying armor, and an entire arsenal onboard. This fight goes 90% in Iron man's favors give or take 9%.
Don't go on and even try to argue about prep time, the whole prep time thing is tired with batman and crap already. This is just, ah crap i have to fight this guy scenario I assume.