Main reason for the lack of mobility for places other than US is because of the size of the mobilizable area one can take. Before the formation of EU, Europeans

Main reason for the lack of mobility for places other than US is because of the size of the mobilizable area one can take. Before the formation of EU, Europeans can only move within their own nation, and comparing that to US, you can see the big difference in terms of land size and number of cities to choose from. With that regard, one need some other forms of statistics to compare if there is no such housing prison (which exists all over the world) and how would this different from the current situation.