There's a tragedy of the commons problem. While I think there's nothing wrong with wanting to move your family from a poorer country to the US, if in theory every person who wanted to do this did do this - from every country (Latin America or otherwise) - it'd eventually become unsustainable. At least not without a huge government program to try to manage it all, which may or may not succeed. Another issue is that criminal organizations can try to exploit this for their own gain, to the detriment of all, and it can become harder and harder to detect or prevent this as the rate increases.

Perhaps we'll eventually be in a future where surplus and government and security improvements makes this much easier to manage, and then maybe more countries will start moving to a more open-borders / global union model, but that future is probably at least a century away (probably several centuries). I think we should strive for that future, but that we should also accept pragmatic reality until it happens.

And I do think we should probably increase the amount of families we currently accept every year. Especially war refugees. Totally eliminating national boundaries is very different from that, though.