You need to translate things for an international rollout which takes time. Plus US is a known devil and easier to rollout and look at numbers to fix the glitches.
Sure. But that shouldn't be a reason to not launch it in India, for example. I have never seen a non-english keyboard in my life here.
Very few countries have internationalization as a necessity. For most places, having the app in native language is a plus, but most people still frequently use the web in English.
I mean, Instagram could figure all the rollout challenges with a single digit amount of people. One would expect a post-IPO company to do so too.