It's not about foreign relations but how long the queue is.

The current date for India (Employment-based green cards) is most backlogged, followed by China, Mexico, Philippines, and Others (Others being its own category).

https://travel.state.gov/content/travel/en/legal/visa-law0/v...

I saw it first hand. My Indian colleagues mentioned that their queue to transition from H1B to green card is impossibly long. It’s just how the numbers work. There are just too many Indians applicants and not enough seats.

This is presumably about the per-country limits on H1Bs- i.e. most countries aren't hitting their quota, so if you apply for one as a citizen of most countries, the wait is comparatively minimal.

What do you mean? My green card application has been pending for 9 years. Based on current projections I won’t get it in less than 100 years or so. Indian. This is a well known fact.