Ask HN: US users, or Global?

I work for a startup who's current main source of revenue is advertising based. We are leading in our space in the US, but lagging behind some competitors globally. Given how we all make money, I think this is a pretty good situation to be in.

What do you think, would you rather be leading in the US, and other more highly monetizable markets (Germany, Japan, UK, etc), or be leading in an absolute, global scale, even if a good chunk of your traffic won't necessarily bring revenue?