Literally every other Google product is America-first, just no need to market it as such.
A lot of users may prefer a locally-branded competitor because they feel it is properly tailored to their needs and culture. (I've specifically heard Yandex understands the interests and needs of Russian-speaking users better than Google, which is not a shock.) Presumably, specifying "India-first" is intended to convey that these apps are developed specifically for Indian users and their needs.
Oh, I understand this completely. It makes perfect sense for Google to focus on an emerging market to become a monopoly there, and I feel it's a fantastic strategy.
What I'm more curious about is why an Indian-first focus is met with fanfare and acceptance, while an American-first focus is met with derision and contempt against something anti-globalist, and that these two opinions often come from the same group of people. I just find it an interesting dichotomy.
The language is preloaded with a lot of existing conceptions about the state of the world currently, and the sort of people who use each set of terms.