One of the reasons why the US was, for a very long time a place where no one had to carry "papers" and show them on demand, was the Naturalization Act of 1790 -- passed by the First Congress, which included many of the Founders, and which was signed by George Washington. This law defined who could become a citizen of the country: only people of European race. Therefore one could easily see with one's own eyes who was alien and did not belong here, and be right 95% of the time. No papers necessary.