[falsestprophet]

"Should an accident of birth(place) be the most import decider?"

There is a school of though that it shouldn't. Many countries confer citizenship jus sanguinis (by descent). Is that system easier for you to understand?

Citizenship conferred jus soli (by place of birth) arose at a time when people were less mobile and less likely to acquire citizenship by "accident of birthplace" and when there were few practical benefits to citizenship in any case. It seems entirely outdated.

Modern nations belong to their citizens who are free to vote for representatives that write laws to benefit citizens and their children.

I doubt you'll have any luck convincing the people of the United States to give away their kingdom or taking it by force.