Not to take away from the rest of it, but there is a very new process for L2-3 certification in Europe. As far as I know, only Mercedes has completed it and released a product (with TUV Rheinland), but TUV Sud is also offering homologation services for European type certification. The L4+ process for Europe is still in working group, with standards expected to be released next year (and 2025 for the UK).

Manufacturers are all pursuing self-certification in the US because regulators have been unwilling to answer petitions either way or commit to firm guidelines.