USA has the kinds of land that cannot support so many people. This is not the issue with India. Their land is abundant in food and shelter resources, the only elements required for thriving societies.

The USA (including Alaska) has about 3 times the land area of India, so India has about 4 times the population on 1/3 the land, or 12 times the population density, but I don’t think even that implies India cannot support its own population.

Their GDP per capita is about 1/30th of that of the USA, or about 2/5 of that of the USA per km², and I think that’s a better way to approximate land needed than raw population size.

Except India is ~1.3M square miles...