EU is still pretty balkanized when it comes to rules and is a headache for businesses especially when compared to the US.

The EU as a whole is much more consistent than individual countries, in fact, standardization is one of it's biggest strengths.

I used to work for the national vehicle registry in my country. European vehicles were easily registered using standard European "Whole Vehicle Type Approvals". Each new European car came with a type approval number linked to it's info, no problem.

American cars were a nightmare. Every new vehicle type came with it's own adventure of Googling or otherwise gathering information about the vehicle (number of doors, engine size etc...). Just no standards whatsoever. Horrible.

That is not true. Each state has different regulations, that's why the article says "moved to California" and not just "moved to the USA". It's possible that UK law is incompatible with other states. The USA has as many or more different regulations than the EU, as lobbying is very strong in America.

is this really the case though? it seems state law results in a ton of balkanization in the USA aswell.

bigger barriers to doing business is probably cultural moreso then rules themselves.

Everyone remembers that "balkanization" refers to chopping up a nation into pieces (Balkans), right? So it's funny to see nations and multi-nations groups, who often sign treaties to "rationalize" rules, referred to as Balkanizing.

They're trying to improve that but it impinges on member state sovereignty so it has to be delegated by them. It will take time.