What happens once charter cities have a large enough population to influence elections and change direction of the country in objection of the citizens of that

What happens once charter cities have a large enough population to influence elections and change direction of the country in objection of the citizens of that country? What I don’t understand is why we don’t treat these mass exodus of people from one country to another country like we do datacenter failovers and failbacks. Give people refuge, let them carry on productively with their life and the condition is that they failback once the situation has stabilized in the country they fled from. To allow a select few to stay, you can create a merit based program based on contribution to adopted society and assimilation to provide an incentive to become part of the adopted host country and be allowed to stay instead of failed back. Without failbacks, we absorb good people willing to work for a better life and deprive that country of those people long term. That never allows those countries to get better because most of the good people leave and never go back. Failbacks would be the healthiest form of nation building since it would be done by citizens of the country in need of being built up. Furthermore, refugees should not change the country that graciously hosted them in a way that many of the citizens of that country dislike. That’s being a bad houseguest.