This is really ridiculous. There are many successful EU vendors of defense technology to the US military. Safran, Schmidt & Bender, Heckler & Koch, Saab, Glock, Fabrique National -- there is a long list. The USA has built real partnerships in these areas.
One amusing example is the C7 and C8. These are AR-15 (M16) variants made by Colt Canada and adopted by the militaries of the Netherlands, Denmark and Norway; and used by special forces in the UK.
Where are you getting your information from, that the US wouldn't allow wouldn't allow EU tech companies access to the US defense market?