If the Church is for open borders it is deluded. I see nowhere in Catholic teaching that says countries do not exist. That Catholicism is an universal religion does not mean the Church does not obey the laws of countries. That would be chaos. And I seem to remember that this Pope just squeaked up about the invasion of Europe this week, if I remember correctly.
Render unto Caesar, someone said...
Countries are just an extension of private property which the commandments promote. If we did not have countries we could not have governments (which the Bible also promotes) and there would be nothing but constant turmoil and the law of the jungle.