Alright, time for some back of the envelope calculations!
A maglev line between Chicago and Atlanta through Indianapolis, Cincinnati, Louisville, Nashville, would stretch about 1200 km.
Assuming a top speed of 500 km/h and a time penalty of about 10 minutes per station along the route and a 5 minute penalty for the departure and destination stations, the ride would take 1200/500 - (5+10+10+10+10+5)/60 = 3.23 hours, which would be quite competitive with air travel, based on travel time alone.
I'm afraid the numbers would get rather bleak once we start to talk about the financial viability of the project. Generally, you get the most societal benefit from infrastructure projects that offer attractive options for day commuting, so any tax subsidies ought to be focused on such projects and not on projects that merely offer attractive options for weekly commutes or one-off journeys.