No. Mexico is an independent country. New Mexico was acquired during the Mexican-American War (1846-1848)
You only need a valid passport to enter Mexico.
No Mexico was never part of the Union, Texas which gained independence from Mexico was a slave state and got annexed in the US together with a free state to create equality in congress.
Mexico
New Mexico was the 47th state admitted to the US on January 6, 1912.
It would have to enter as a slave state. And they didn't want a war with Texas and Mexico.
Having a passport and/or Visa is a legal way to enter the U.S. from Mexico.
No
Mexico is an independent country. It is not a state of US. It has nothing to do with the US. It is outside the United State's jurisdiction. Only New Mexico is in the US. It was admitted as the 47th state in 1912.
The state of Vermont prohibited slavery in 1777. As the US Constitution was not ratified until a decade later the answer is yes, Vermont entered the Union as a Free State.
The Missouri Compromise of 1820 allowed a slave state into the union when alternated with a free state. The compromise allowed Missouri to enter the US as a slave state and part of Massachusetts was divided to allow the entrance of Maine into the US as a free state.
In 1820, a portion of Massachusetts became the state of Maine. This was part of the Missouri Compromise of 1820, which allowed Missouri to enter the US as a slave state and Maine as a free state.
Your birth certificate will not help you. You can enter the US from Mexico with an "enhanced" US drivers license, but only if you are traveling by sea or land, not by air.