My very biased opinion is the best pike (probably the best freshwater) fly fishing in the lower US is in Michigan. Pike are great, and so are the other options swimming around.
Lake St. Clair is most well-known. It is cheap to fly and stay, you can rent boats (several marinas, check out Middle Channel Marina...they have lunds), and lots of information is available. The river is also loaded and you can fish from the bank in many places.
2nd choice is Houghton Lake, about where your middle finger meets the palm on your right hand. Easy drive from Detroit, Grand Rapids or Traverse. Cheap to stay and multiple places with boat rentals. Plus, you are close to world class fishing...the Au Sable is less than an hour, the Manistee about an hour, blah, blah...
Check out Michigan DNR and look for pike and special regulations...a few size limits for a handful of places and 5 fish everywhere else. There are pike everywhere.
Again, super-biased. Pics from NW Michigan in October with brother-in-law.