Cómo fue que México se incluyó en los organismos internacionales

https://photius.com/countries/mexico/government/mexico_government_membership_in_intern~496.html#:~:text=Mexico%20also%20is%20a%20founding,Development%20(OECD)%2C%20the%20Asia

Given no context as to what "border states" are, I am going to assume you are referring to the states that marked the border between the union and confederacy during civil war times. I believe that these states were as follows, Delaware, Kentucky, Maryland, Missouri, and West Virginia as it separated from Virginia at this time.