Is Boeing too big to fail?
Yes.
In crisis they will be rescued by whichever administration is in power. As the only commercial airliner manufacturer left in the USA, even before you count their military contracts. It does not matter what they state at the time: money/jobs/national security (probably all) there is no doubt that Boeing will not be allowed to fail. The 'always free market' of the USA will do what it always does and good luck to them.