It might not be widely known but the NYT Bestseller list is curated list.
It would be nice if someone could find a couple of examples of non-controversial books that made the top of other bestseller lists but that the NYT excluded because they weren't published in the US. That would make it a lot easier to defend the accusations that they are using "Canadian published" as an excuse to keep a book off the list they don't like. There have got to be several publishers in other English speaking countries with very popular books that don't have any US presence that still sold well here.