Interesting idea but impractical. How do you pay for common services? How do you govern?

Those are just two questions where the answers lead to complex discussions about work, pay, responsibility, common services, etc.

Borders are necessary for many reasons. First and foremost, the common needs of an area differ from area to area.

What one really wants is freedom of movement across borders without artificial constraints to movement. And, those meeting simplified residency requirements would have voting privileges in a given area. Yet, even allowing for that is fraught with potential problems simply because people would be free to vote for expensive projects and then leave, thereby removing themselves from responsibility for paying for those projects.

In short, without borders and without some form of residency and taxation, governance and common projects that benefit all those living in an area become very problematic.

Borders are outmoded, with travel worldwide so easy.

might?