No. American citizens don't require a visa to enter Mexico. All you need is your passport.
Yes, you need a passport to go from the U.S. to Mexico because Mexico is not part of the U.S. If you were going to a U.S. territory and you were a U.S. citizen, you would not need a passport.
Yes, you need a passport. If you are leaving the USA and going to Mexico then you need a passport.
If you live in Mexico then no.
Yes, you need a passport. When you travel to other countries by plane,car,ship you should always have you passport along.
Yes
No. New Mexico is part of the United States, so you don't need a passport. :)
Yes, you always need a passport when you travel outside your country of origin.
Yes.
Yes you do
Yes, you do.
Yes
Yes, they do.