I don't think there is much argument that the U.S. supports much more of an immigrant and minority population than most other countries.
Canada has 1/5 of the population born outside of Canada (largest in the western world). And its not only Europeans. Europeans only make up 40% of these immigrants. In fact majority of new immigrants are coming from China/India/Pakistan/Philippines. Surprisingly this is only 1/10 for the US.
I got this from http://www.thestar.com/News/Canada/article/282347.