That's a definition you just made up, which has no precedent and is clearly untrue.
I can cross a dozen borders in the EU without so much as slowing down. I can sell my house in one US State and move to another without asking for permission.
It wasn't until World War 1 that passports for international travel became common in Europe.
Don't let the xenophobic posts on social media trick you. Immigrants in the US are factually less likely to commit crimes than born Americans, look it up. They've just repeated the lie so many times that people have accepted it.
The term combines two concepts: Nation: A group of people who identify as belonging to a shared community. State: A political entity with a defined territory, a government, and sovereignty over its internal and external affairs.
I would argue this requires at least some sovereign control over borders.
The EU defines their borders as a bloc. States are not nations - and that’s one of the reasons why.
Border control is an important expression of state sovereignty. If you have zero controls the state would experience net migration until conditions declined below the global average and nobody wants to move there anymore. That’s pretty self evident, it’s how economics works and how systems maintain an equilibrium.
Both legal and undocumented immigrants in the US show lower incarceration rates than native-born Americans in major studies; the picture in Europe is different, with clear overrepresentation for non-Western and asylum-related groups. Fiscal impacts depend heavily on skill/education level rather than legal status alone, with low-skilled migrants (legal or not) more often a net cost over their lifetimes.
So control over borders is important, and having standards is a good thing.
There is no magic soil. A nation is the people who make it up. Bring in the violent, stupid, and culturally incompatible people from the shithole countries they are trying to escape and things will trend downwards to some average between those terrible places and our desirable countries. That’s not racist our xenophobic, it’s acknowledging the facts.
People are not equal. Countries are not equal. Education and culture and religions are not equal. There are better and worse versions of all of them. Again just facts. To ignore that is to live in fantasy land that doesn’t exist in the real world.
I have traveled to nearly 50 countries. I have lived in the developing world. My ancestors have had to flee countries and been refugees. I know what I’m talking about. You sound very idealistic and naive.