Since last fall, the ten year Canada has risen about 75 bps .... mortgage rates have also gone up, albeit probably not by 75 bps (should be priced off of the 5 yr Canada).   I am pretty sure that what your bank pays you on your savings account has not budged -:), so yes, spreads have widened somewhat.

The NIM at the US banks (with 30 year mortgages...) suffered a lot more than at their Canadian counterparts....and have probably benefited more from the post Trump bump iun rates.

Yes, both Canadian and US banks "securitize" sizable amounts of their mortgage books, albeit much less so in Canada (which is part of the reason that the standards of the Canadian banks were higher going into 08/09....i.e. if the bank is gonna hold onto your mortgage, they "care" a lot more about whether or not you are going to default).  Institutions (including pension funds etc.) are the big buyers of mortgage  backed securities.