This isn't quite as drastic as it sounds; the US has long operated what is known as CRAF - the Civil Reserve Air Fleet, which means that US carriers are paid a certain amount to have certain suitable aircraft (Pan Am had most of its 747s fitted with side cargo doors, for example) available when it needed to engage in military action.
Frankly, I don't consider this an issue that should cause a delay; if aircraft belonging to a certain airline are required by the CRAF in times of war/ emergency, I don't see how this would change as a result of a foreign airline having an interest in the carrier.
What I really wonder is, if US businesses and airlines aren't willing to buy into their airlines, many of which are in Ch 11, why would foreigners necessarily be? Much of what is being argued about is potentially academic and unlikely to come to fruition and frankly, I've long suspected - in the case of BA and AA - that part of BA's strategy in suggesting a buyout of AA - is to ask for something it knows is a non-runner, with the hope that it will cause such a political melee that the whole O/S issue will die. BA's bottom line is that it DOES NOT WANT any change to t/a access to/from Heathrow - no CO, no DL, no BMI, no one else.
And as ever, guess who gets stuck in the middle? Yep, it's us as usual. Poor Aer Lingus and Ireland, with a government with scant interest in air transport issues unless it is actually forced to do so.