This is a very idealistic goal, but we still have no solution to issues like how the state would balance the books if the population is in constant flux. If the number of contributors suddenly decreases or the number of consumers of social services shoots up, then the state will simply go bankrupt.
If you allow total freedom of movement, you're basically creating a system similar to a business where you have zero predictability and control over your income and your costs.
In the US you are completely free to move and work in any state you want to (and a geography in the same order of magnitude of all of Europe), and it doesn't seem to cause the mayhem you suggest -- and mind you, most gov't spending takes place at the state and local level.
But you always pay taxes at the federal level, which distributes some of that income to states. Also the individual states have the mechanism to recover taxes you owe them from previous years and to pursue you for whatever violations you have committed. Additionally, state residence does exist as a concept and it is tracked in the form of state ids. It's true there are no borders but you are required to register where you live, you pay more tuition to state unis if you're not a resident of the state, etc. Just because there are no borders doesn't mean there's no control.
You can't really compare the US state system to different countries that are openly hostile or may not even talk to each other (e.g. US and Russia, or US and North Korea) and expect to have the legal cooperation that could enable freedom of movement.
>You can't really compare the US state system to different countries that are openly hostile or may not even talk to each other (e.g. US and Russia, or US and North Korea) and expect to have the legal cooperation that could enable freedom of movement.
That reveals a fundamental difference in how we see the world. The hostility which you mention is real, but I see it as a byproduct of the kinds of walls and separation we artificially place between ourselves. Let's not forget that same animosity existed between the U.S. and China, and more commercial relations reduced those tensions.
I fundamentally believe that the PEOPLE in the U.S., Russia, and yes, even the North Koreans, are fundamentally good. These artificial barriers we palce between one another create this us v. them environment, and that leads to this hostility.
How many times don't we hear complaints about "our jobs going oversaas," for instance? Mind you, many of the people voicing those complaints are also people who loudly advocate for increased job opportunities here at home. The lack of empathy for people in other nations is real. But it is created by these restrictions.
As the article states, there were no artificial barriers before 20th century. But we still had plenty of horrible wars. So I disagree with your premise that removing barriers will lead to more harmonious relations.
In fact, the barriers seems completely irrelevant to the relations between different societies. We have had atrocities without them or with them.
If you allow total freedom of movement, you're basically creating a system similar to a business where you have zero predictability and control over your income and your costs.