"Population size, the EU is a much bigger market meaning it is easier to align standards etc. "
Exactly. Just happened to come across this in relation to a project I'm working on:
The Australian Design Rules (ADRs) are national standards for vehicle safety, anti-theft and emissions. [...] The Australian Government's policy is to harmonise the national vehicle safety standards with international regulations where possible and consideration is given to the adoption of the international regulations of the United Nations Economic Commission for Europe (UNECE).
I'll grant that EU >< UNECE but it is a good example of standards harmonisation.