Right now, a lot of companies start in the US because the US is the best place to start. 330 million people, one language, good profits, etc. But, a punishing tax might mean that the profit margin is much less than 10%. 10% is a huge profit margin for most businesses, so it might drop from say 5% to 1%. At that point, Europe looks a lot more promising as a place to start. 450 million people, for the most part it's one regulatory zone, you do have to have things in multiple languages, so that's a bit difficult.

Then, after Europe there's east Asia: Japan, Korea, Singapore, Taiwan. Then slightly poorer countries like Indonesia and India. Maybe South America next.

The US would be near the bottom of the list if it was the only country with a punishing tax rate.