Having multiple, smaller groups of people inside the USA also assists integration - instead of being able to fall back on a parallel society, migrants will be forced to integrate and learn English.
Plus, just like the Olympics, diversity makes things interesting. Having (qualified) people from Belgium, Poland, Kenya, Thailand, Japan, Colombia, Mongolia (for example) is more interesting than just India, India, India, China, China, China.... A broader pool of migrants also helps US businesses expand worldwide.
Finally, the schemes should also include a minimum 55% quota of women, from each country. This ensures that any visa scheme does not become completely dominated by men, and addresses past imbalances.