I don’t think many rural counties could financially support the full cost load of construction and then maintenance (including all the rebuildings that have occurred since the 1950s/1960s) of even one interstate crossing the county.
Yes, the cost could be a burden. Maybe the state could ease the pain financially and share in the maintenance work. The point is to keep the feds away from dictating how and when things are done. Hopefully there are ways to do that.