In the case of the U.S., once someone enters one of the
states, that person can move from state to state without having to show a visa
or passport. The open borders correspond to the states that are members of the
United States. In the case of the E.U., however, the open borders do not
necessarily dovetail with the states that are members of the European Union.
This presents problems that do not exist in the U.S.
