Those four countries have very different quota problems though: folks from Mexico and Philippines face a long wait in family immigration, mostly to bring their kids & siblings to the US ( https://travel.state.gov/content/travel/en/legal/visa-law0/v... ), whereas Indian nationals also face long waits for employment based green-cards.

Noting that you can always use your country of birth or your spouse's country of birth (cross-chargeability) for an employment-based green-card, my understanding has always been that Indians have large preference (or face large pressure) to marry other highly-educated folks that they often meet in the US but are also born in India that other immigrants just don't face as much.