My facts based argument goes back to the original parent discussion that you joined, which is: the US is considerably more diverse than Canada and that that is due to very different immigration policies over time. I've overwhelmingly backed that up.
Would poor people have immigrated out of Detroit and into Canada as Detroit collapsed, seeking a drastically superior social safety net, free universal healthcare, etc.? Hell yes they obviously would have.
> You'll have to cite a source stating that the growth in those populations is from internal movement.
You can't actually believe the US has historically lacked for internal movement (in fact it's only very recently that that has been the case).
California's population in 1960 was 16 million. The US total hispanic population in 1960 was 6.x million. As recently as 1970, California's white population was nearly 80%. In 1970, 16 million of California's 20 million people were white - how did they get there? Millions of people moved to California from other states, famously, in the post WW2 era.
Las Vegas, which makes up a quarter of Nevada's population, is 44% white, 11% black and 7% asian today. How do you think those people all got there? The Las Vegas population figure was 8,422 in 1940.
I'm certain I don't need to cover Arizona (boomed internally similarly to Nevada), Texas and Florida. Florida has very famously seen vast internal US migration as older people flooded the state over decades.
