Where did the Americans and Arabs fight on 9-11?

Answer 1

Americans and Arabs did not fight on 9-11.

Arab Muslim extremists hijacked planes and committed an act of terrorism against the United States. Fights occur between combatants representing two sides of a larger conflict. The extremists represented only the views of Al-Qaeda and, even they, did not claim to represent the "Arabs" but a global Islamic Caliphate.

9-11 took place though in New York City, where the Twin Towers collapsed, Washington DC, where the Pentagon was attacked, and in a rural area of Pennsylvania where the passengers of that plane heroically prevented another building (most likely the White House) from being hit.