Canada does make it pretty easy to sponsor a spouse, common-law partner, or single children under age 22 for permanent residence. In fact it's far easier and faster than the US equivalent.

You're right about the relative percentages between the countries, but that's simply because the US makes even skilled economic immigration far more difficult than Canada. All common kinds of immigration are easier in Canada, though neither country makes it truly easy as was true more than a century ago.

You're right that there are only very narrow cases where Canada allows sponsoring siblings, unlike the US. But those kinds of differences go both ways: for example, Canada allows common-law partner sponsorship after 1 year of cohabitation without requiring marriage, whereas the US doesn't. (I am not referring to what the US calls "common-law marriage" but to a type of relationship that continues not to be treated the same as marriage under Canadian law, except where specifically indicated.)