What obligation do I have to sign on to exclusionary immigration policy. The southern border is just a line in the sand. No party (US or Mexico) has a reasonable claim to the land to begin with.
If a state’s borders aren’t enforced, either those borders are not in fact the state’s real borders, or the people residing within those “borders” are living in a failed state.
This logic isn't remotely sound. It's a ridiculous false dichotomy. There's a third option: It's a normal state that hasn't built walls around it like some kind of medieval walled cities. Do you think every state that isn't completely walled off (there are basically none besides the Vatican) is "failed"?
Who said anything about walls? A state’s borders are defined by the land area over which it upholds its own legal system. If a state’s legal system is unenforceable within its so called “borders”, then by definition those are either no longer its borders, or the people living within the land area over which the state’s legal system cannot be enforced are living in a failed state. The borders will have become disputed in that case.
And as I said before, the southern border is mostly made up. People crossed it for thousands of years without some crappy wall in the way. They will continue to cross it even with a wall.
Building a wall is just a dumb move regardless.