This consequence is so obvious one must assume it's part of the calculation. The US has an unsustainable military budget. Their bet, as I see it, is that the US will see a net positive from the shrinking of the military industrial complex and reduction in expenses defending Europe.
The US has a big enough military to keep the contractors afloat. Also, keep in mind that despite Europe having good technology in many areas, it will take many years, if not decades, for Europe to have real competitors that can match the American equipment in key capital intensive areas.
