CHARLOTTE — Visitors to Charlotte often travel from the airport to the city center via the Billy Graham Parkway. It can startle the first time, seeing a public roadway named for a major religious figure. But you get used to it once you’ve lived here awhile. You realize how much the region takes pride in its native son, though the life and history of the man called “America’s Pastor” illustrates — in even his own judgment – how tough it can be to maintain a separation of church and state. Should America have a pastor at all?