You don't have to do anything. You don't lose your citizenship by living in different country. You lose it when you become a citizen of that country.
The Treaty of Guadalupe Hidalgo (and Mexico definitely got the short end of it).
Only if you apply to become a Canadian citizen. Once you get residency in Canada you can apply for provincial healthcare.
The North American Free Trade Agreement (NAFTA for short).
You probably mean Gila monster. This short-tailed lizard lives in the American southwest and Mexico. It is poisonous.
The North American short face bear ranged from Alaska and Canada to central Mexico and all across the region that is the United States today. It was the most common of early North American bears and a majority lived in present day California.
Una "chamarra"
The American bobtail has a short tail because the short tail gene is more dominate.
That depends on what your American wants.
The official name is "United Mexican States" (Estados Unidos Mexicanos).
A monarchy, led by Maximilian I of Mexico. It was short-lived, though (1864-1867).
Lee fought under General Wainwright in Mexico in the Mexican-American war. Lee was very instrumental in assisting the American forces in marching to, and taking over Mexico City. Wainwright was made governer of Mexico for a short time. One of Lee's brother officers in this campaign was Ulysses Grant. The two later would be leaders on opposing sides during the US Civil War.
Frederick Kaufman wrote "A Short History of the American Stomach".