Actually, there are tons of illegal Bolivians and Paraguayans in Argentina. The people are not too happy about it, but, much as is the case in the US, the government isn’t doing much to keep them out. Ditto the Nicaraguans in Costa Rica (over 20% of the population of Costa Rica was born in Nicaragua, and remember that Costa Rica has a very genrous welfare state).
I’m sure there are governments all over the world that look the other way when illegals slip into their country. That’s because either the business elite want cheap labor or the government wants a bunch of dependent voters.
But my point is this. Are borders just imaginary lines on maps which in reality we all have a right to ignore? Do you or I have a right to go to any nation we want without documentation, and not bother to follow the immigration laws of that nation? Do we have international open borders?
No one will answer that question because they understand the ramifications of it. So they have to at least pretend to support some kind of border. But at that point it falls into the “some illegal aliens are more equal than others” category. If millions of white Americans flooded into Haiti to the point that they outnumbered the blacks there and voted them out of power, the very same people who are screaming for us to “tolerate” illegal migration into America would call it genocide.