All manufacturers and all suppliers are subject to parts problems. To imply nationality is a major influence on quality of product, especially where those products are certified by one of the major authorities and then cross-approved by the others, is a bit much.
As a completely non scientific survey, I just reviewed the FAA's "new" AD listing (all ADs in the last 60 days)
Boeing has 8 FAA ADs issued or revised in the last 60 days.
Airbus has 9.
I don't consider that a statistically significant variation, and certainly would not conclude anything about OEM or supplier relative quality from it.