Let's say there are on average 10 "viable" presidential candidates per election cycle every 4 years. Over a 40 year time-frame (You can be elected president during approximately 40 years of your life, from your late thirties to your late seventies), there are total 400 viable presidential candidates.

If 99.99999% of Americans have 0% chance of becoming president, that means you're saying only 3180 Americans have greater-than-zero chance of becoming president.

I suggest it is a little more than that. Millions of Americans, aged 10 and under, have the potential to work towards becoming first a mayor of their small city, then a mayor of a big city, and then finally have a small positive chance of becoming president. If you have greater than zero chance of becoming a person who has a greater than zero chance of becoming president, then you have a greater than zero chance of becoming president, period.

I suggest the number of such people is surely greater than 3180.