The US is far from being the most diverse country in the world. Even Canada is more diverse.
because Americans are counted as minorities there.
Please bring up the European countries that count other Europeans as minorities.
I don't know of any other country that defines diversity like the US does. "White, black, Hispanic, asian, native, other". we are literally too diverse to care which part of Asia you are from, which part of Europe, Africa, S. America you are from. Every other nations tracks that, we just say "lol, welcome to America whitey".
Immigration to the United States - Wikipedia
we had 43 million immigrants in 2015. I think this is a running total, no idea if they track people who died. That's equivalent to the population of Argentina, the 31st most populous nation in the world.
List of sovereign states and dependent territories by immigrant population - Wikipedia
we have 30 million more immigrants than the next closest country. We have more immigrants than the next 4 combined. maybe even 5 but I didn't feel like doing that much math.
just be sheer numbers we are the most diverse.
that's even ignoring the specifics. unless you believe the people we are getting are LITERALLY ALWAYS the majority in their home country. I would argue you probably see at least their own demographic breakdown represented in those who come here.