Sure Blink is a fork of WebKit which is a fork of KHTML. But that was 1000 years ago. The biggest contributors by leagues are Google and Apple. Those are US projects. Trying to say they are European is nuts.
LibreOffice is German though and while OpenOffice was from Oracle, it was based on StarOffice which was German. So, the EU can claim that one.
NextCloud is a solid example too.
And, of course, there is SUSE.
Igalia (Spain) brings Servo (web browser) and Chimera Linux too.