US WWII military aircraft like the B-17 were owned by either the US Navy or the US Army Air Corps.
The Army Air Corps became the US Air Force in 1947. The Air Force had a fire in the early 1960’s which destroyed all their ownership records for lost aircraft. The result of this is that the US Air Force has officially abandoned all lost Army Air Corps and US Air Force aircraft lost before about 1960.
The US Navy has its’ records for all WWII aircraft and retains ownership under the Sovereign immunity no matter where or how lost.
So, if the aircraft was owned by the US Army Air Corps, it is free to go after as far as the US Army or US Air Force is concerned. But you will need to prove that ownership, and make sure that it was not owned by the Canadians or some other organization. Also, after the war a number of aircraft passed into private hands, so if it was lost after the war, it could be privately owned or the property of an insurance company. Photos of the tail numbers would suffice to determine who owns what.
Once that is cleared up, you fight the Canadians and the archaeological and/or historical preservation offices – lot’s of luck there.
If you have been able to get past these two hurtles, you have the recovery – you will need to have plans for containment of oils and aviation gas – there will be some, any ammunition which may be found, and heaven help you if there were any deaths involved in the crash with the disturbing a grave or handling human remains complications.
The last thing is to raise the aircraft without destroying it and then getting it to some place where you can repair or curate it. Have lots and lots of money.