I don't think most of your examples are correct, but in any case, not everything has to be started in the USA.
Private companies running a taxi service (arranged by phone) were widespread in the UK long before Uber, and surely also other places. Why couldn't Uber start there, if the USA was too restrictive?
One Uber founder is American and the other Canadian and AFAIK both lived in the Bay area, so they probably prefer staying where they were. How much harder would it be to get VC funding for a business in the UK? They already had VC connections in the US from prior ventures. Same issue probably true for engineers they could bring on board. The UK is a much smaller market.
Further, I don't think Uber started out breaking regulations. Initially you could only hail black limos and which were licensed. They only started offering rides from unlicensed drivers in response to competition from Lyft. Lyft in turn started as a long-distance ride sharing company which is also legal. So the hurdle for either company to move to the UK was even higher. Moving an established company to a less important market seems far fetched
Private companies running a taxi service (arranged by phone) were widespread in the UK long before Uber, and surely also other places. Why couldn't Uber start there, if the USA was too restrictive?