My (potentially wrong) understanding is that backlogs are often determined by country in order to prevent any particular foreign ethnic group (like China or Ind

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.