It's a factor in whether "219.43 million people" is a lot of people. If that's 219 million people in the US (i.e. well over half the population), that's obviously massively more significant than 219 million people worldwide.

But for the question of anti-trust action it doesn't matter whether it's "a lot" of people, it matters whether it's an insignificant number of people - if there were 10 smartwatch users in the US, the argument "who cares about smartwatch users" could be valid, but it makes no difference whether there's 219 million people in the US or 219 thousand people in US, since even 219 thousand users is definitely much, much more than sufficient to justify intervention.