Most of your options will be out west because that's where the big expanses of public lands are.
So you're really asking about good mileage point to point trails. You can usually work out a route in many places that might not be one trail but in the end does it matter if you link 5 trails or just one? Most long distance trails are just old shorter trails linked together and giving one name anyway. The Colorado trail is a good example of that. Speaking of CO, Telluride to Moab is a popular point to point. I can't remember the link up but it's become a popular ride over the years. Check out different CDT sections. Tons of point to point options. Most of your options will be out west because that's where the big expanses of public lands are. Public lands are so fragmented and small in comparison on the east coast your options are much more limited.