Double digits
A rating from Switzerland on BoardGameGeek has placed Ambition into the double-digit club. There are now 10 countries in which Ambition has a verified presence, though probably many countries not on this list should be, as I'm including only verified places. They are: Australia, Canada, Finland, France, Germany, Hungary, Japan, Switzerland, United Kingdom, United States.
There is further, but unconfirmed, evidence indicating a high likelihood of Ambition presence in six more countries. Some of this, however, is admittedly speculative (such as Mexico, included on account of the reported "Orange County cluster" of players in southern California).