How Can I Get A Visa To Travel To Us From Mexico?

To travel from the US to Mexico, you need a US passport to get back into the USA.  But you may also need a FMT document (a type of tourist permit) inside of Mexico, depending on how long you stay and where you go.  You'll need Mexican insurance and documents for you car if you take one.  You also need some additional documents if you take a pet.   If I find a good website that describes these better, I'll post it here.

From www.apu.edu
U.S. Citizens do not require a visa or a tourist card for tourist stays of 72
hours or less within “the border zone,” defined as an area between
20 to 30 kilometers of the border with the U.S., depending on the location.  U.S. Citizens traveling as tourists beyond the border zone or entering Mexico by air must pay a fee to obtain a tourist card, also known as an FM-T, available from Mexican consulates, Mexican border crossing points, Mexican tourism offices, airports within the border zone and most airlines serving Mexico.  

Mexican nationals that wish to travel from Mexico to the US should seek advice from a US embassy.