I too am vigorously in favor of communities right to expel people. Being born to American or Saudi citizens shouldn’t give any special rights if you the community decides they’d be better off without you.

Less sarcastically we have no evidence that democracy, unrestricted immigration and welfare states are compatible. I’ll happily bite the bullet and see massive restrictions on immigrants’ and even their children’s rights to access the state’s largess as the potential welfare gains are enormous. But that’s probably among the least important and disruptive changes of open borders. The EU, Canada or the US could easily attract immigrants in similar numbers to their total current inhabitants. You think their politics could cope with that well? California can’t even force the amalgamation of the Bay Area into a single city or copy working models of dealing with the homeless. The US can’t copy international rail infrastructure. The EU can’t get it together enough to pay Erdogan his bribe to not let the Syrians into Greece and the rest of the EU. Canada barely has an internal market in goods and services. Politics doesn’t work very well as is. How will it work with a sudden huge increase in non-native non-citizen population?