It's my experience that since the idea of 'standardisation' within Europe began the bureaucracy with gaining acceptance of PMA & STC parts ex USA has got worse.
Yes this is really bizzare but IMHO this is EU-USA political posturing and the long term path must be that this reverses.
To suggest the contrary is to pretend the USA does not exist, that we are not flying planes which are either made wholly in the USA, or have airframes made elsewhere which are then stuffed with 90%+ of stuff that is made in the USA....
Let's be frank... you buy a U.S. made part which comes with Form 1 (EASA-1 form). How do you think that part acquired that magical European document??
It's an industry secret, revealed by me here for the first time.
You have a company, here in Europe, which has purchased (yes purchased, like you purchase an ISO9000 approval) the authority to generate EASA 1 forms.
The part arrives, with some kind of CofC (an 8130-3 but could just be a delivery note with a batch / serial #) at this company. There is a little man in there (all people in certification are little men, usually below 5ft4) who looks at it and writes out the EASA form.
The company then resells the part with a 2x markup (and the EASA form).
I once paid about £11000 for a Hartzell prop with a JAR-1 form which could have been had from the USA for $9000.
This company could generate an EASA 1 form for a Mars Bar (if it came to them with a suitable traceability document).
EASA insistence on Form 1 is going to bring the whole aviation business to its knees and everybody (except the little men, whose employers are busy lobbying EASA for the introduction of "standards"
) knows it.