[hayst4ck]

My (potentially wrong) understanding is that backlogs are often determined by country in order to prevent any particular foreign ethnic group (like China or India) from becoming residents in such quantities that assimilation to American culture is unlikely.

Pragmatically you can already see the effects of anti foreign ethnicity backlash in national politics, so it does seem like something that needs some level of management.

[Sophie_Alcorn]

The backlogs do exist, they're based on the Immigration and Nationality Act of 1965, and they are for green cards specifically. In the employment-based immigrant visa categories, they specifically apply to people from India and China.