For better or worse, 'american' is the defacto standard on the internet, but please remember that only a small percentage of the global population is USian the in all probability the person you're speaking to isn't from the US.
Disclaimer: Not English. Not American.
UK, Australia, new zealand Canada already add up to a sizeable chunk of the US's population. Then add in 1% of India, or China (I assume some proportion has access outside the great firewall) and you've got a population bigger than the US.
US: 331.9 million
UK: 67.33 million AU: 25.69 million CA: 38.25 million NZ: 5.123 million IN: 1.408 billion * 0.01 = 14m
Point is some very small percentage of the rest of the world is going to dwarf the US. Yes the US will be the single biggest demographic but less than 50% of the total.
I haven't been able to find many solid stats, but eg English language Wikipedia, the US has 22k active editors out of 59k total.