Canada in particular has sought to exclude much of US programming in support of its cultural integrity and protection of native production.
That hasn't been the case in ages. The CRTC rules are now so lax that stations can get away with using reruns of Degrassi, Corner Gas, Schitts Creek, Just for Laughs, Comedy Now or Cash Cab in the morning to meet their CanCon quotas, and the rest of the day most of the schedule is American programming.
There are times where the Canadian networks air primetime programming before the USA, especially on the Atlantic stations where they have to air news at 11pm AT/10pm ET, so the 10pm ET show airs at 8pm AT/7pm ET. They also have 7pm ET hour premieres in the rest of the country for some shows if there's a schedule conflict, which CTV did for Bob <3 Abishola and Night Court and Citytv did for Next Level Chef, Hell's Kitchen and Law & Order. Global used to do it too for The Simpsons before it moved to Citytv and CHCH.
My question is whether (and to what extent) Canadian content is (officially) restricted in the US. I'm guessing a lot of it would simply come down to they don't have permissions to market content outside country, and not restrictions coming from our gov't in the way they do up north.
If you're talking about the official linear streams and full episodes on CBC Gem, CTVgo, Global, Citytv, pretty much everything except news streams are georestricted to Canadian IP addresses. It's more of a rights issue since a lot of CBC and CTV originals are now licensed by US networks like CW, Hallmark, Ovation and Up and various SVOD services that specialize in Canadian, British, Australian and New Zealand imports.
For Canadian channels via streaming. On their official apps, the streams for CTV and Global require a pay TV login, the streams for CBC TV and Citytv are available for free, but unfortunately last week Rogers stripped CBC of the streaming rights to the NHL playoffs. CBC News Network is available with a premium Gem subscription. TSN and Sportsnet also have their own direct to consumer subscription services.
If you have a Canadian credit card and access to a VPN that isn't blacklisted, you can try getting FuboTV Canada which has the CBC and Corus owned channels. If you can access Prime Video Canada you can add Citytv+ which will also give you Omni and FX Canada and StackTV which will give you most of the Corus owned channels including Global.
If you're French Canadian, it's a lot easier as Radio-Canada, Noovo, TVA and Tele-Quebec all stream online for free without a pay TV login. In Radio-Canada's case they also have international streams that simulcast the news and any entertainment shows they can stream worldwide.