I dont see it happening US goverment is happy haveing both BAE and Boeing as seprate companys. Mergeing the two would just create a company with two broad of a product spectrum. I see US goverment wanting certain companys to take lead in specific fields and not try and make a US version of EADs. Boeing and EADs are close in size in Dollar/Euro terms but when you compare total market percentages in the domestic defense markets EADs has twice the % of European market as compared to Boeing % of US market.
The Rolls Royce buyout I could see US goverment suporting that but I doubt UK goverment are Europe would allow it. UK by forbiding it and Europe by starting a massive bidding war for company if UK didnt block it at start.
Given that in recent years BAE has invested just about every spare penny of investment capital it has in the USA and has now fully divested itself of Airbus and has for a while now tried to downplay its 'British' credentials, what's the problem? More likely than a Boeing by-out, which would hit regulatory buffers on both sides of the Atlantic, is a dual listing in NYSE. BAE has already moved its armoured vehicles division HQ to the US - a move of the full HQ may not be far behind.