I wonder if this statement is true. The reports I read about Android vs iOS revenue are US market only, or about e-commerce payments.

I'm an app developer and we make a lot of money developing apps that never end up in the app stores. They are in-company apps, both Android and iOS apps.

There is a very big app market that you will never see.

It is mostly 'has been repeated to death so it must be true' statement. The reality, as always, is way more complicated. Outside of the US market, Android and iOS have very comparable high end marketshare. Depending on your niche and your business model, the good choice for your app can vary from one opposite to another.

Outside of games paying customers are increasingly irrelevant in the app store. It's becoming more and more difficult to make an app a profit generator in itself. These days mobile is more about reach for existing businesses. In this world user base counts.

It's also much, much easier to quickly iterate on Android without two-week delays between updates and a capricious review system.

I thought OP was very clear about the serious business reasons they see for US startups to make an earlier and more serious commitment to Android:

1. You will need Android support eventually (to go global, because users demand it, etc.).

2. If you try to add Android support later, you'll screw it up in ways that will be difficult to fix (e.g. porting iOS apps too slavishly, not taking advantage of Android-specific platform benefits, building a corporate culture that treats Android as second-class, etc.), especially since most of the best Android talent will want nothing to do with you.

Because outside US, the majority is on Android.

I've seen this disproven many times. It may have been true early on but I don't think it still holds up.