The EU does seem to willing to reduce itself to a Chinese vassal. That would not improve the situation.
> The EU would also have opposed it if the US bought Russian, Chinese or Iranian weaponry.
This is such an implausible counter-factual that I can't even begin to imagine what would have actually happened. Still, I doubt any more than some "public letters" would have been issued, whereas I'm sure that the opposite would have resulted in actual economic pressure from the USA against the EU/NATO country that would have dared, under any administration.
Likewise NATO countries aren't keen if one of their members gets a leader who rolls out the red carpet to the Russians and threatens to invade other NATO states. It's not like all the members have to do what the US likes.
Here's a Danish vassal MEP saying "Mr Trump, fuck off" https://youtu.be/hASG-hQgk-4
I see the Turks have now changed their mind on the S-400s and I hope the red carpet for Putin folk change at some point too.
Arms trading with China is probably not a good idea at all.
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?