How Does a Border Affect us and Mexico?

What a border does to us is that it separates two countries for both good and bad reasons.
A good reason that a border is made for us is that it keeps the United States an individual country.
A bad thing for us is that if you forget your passport when you go to Tijuana, you can't come back.
(Unless you can actually show your true U.S. Identification or prove you are a U.S. citizen these days)
How a border affects Mexico is that nobody without a passport can cross and many were not born with papers of Identification or a birth certificate making it nearly impossible to be able to get a passport.
Also when one tries crossing illegally, it is very hazardous and can most likely die trying whether of murder, sickness, or lack of water.
A border does many things, some good some bad.
But just think, what would life be like for the U.S. and Mexico without a border?