It also has to do with religion, and local customs. Most latins, south of the border are catholics, and until recently, the pope didn't believe in birth control. There are around 7.5 billion people in the world.1.25 billion alone are in India.
africa is 1.2 billion.
China 1.4 billion.
The USA, only 326 million.
Land mass, US is nearly 4 times larger than India.