Interesting. I would have expected more from Latin America than just Guyana.. but I guess all of those immigrants get to the United States first and decide that's good enough.
I would question a few of these and I live in Canada. There's more Congolese, Somalis, and South Sudanese, but I think fewer Iranians, Sri Lankans, and Guyanese.
It's all very regional. I have never met a Guyanese-Canadian, but I heard Toronto has a huge Guyanese community. Likewise, Vancouver has a large Persian community. Based on your comment, I can guess you live in a Prairie Province like me :)
As someone who lived in Canada for some time, I am surprised by the low amount of French people and of African people in general. In Quebec at least we got loads of them.