Canada, being a sovereign nation independent of the US, yes, flying to Canada is flying internationally.
DHS issued Trusted Traveler program cards, such as NEXUS or Global Entry, are also Real ID. I've used my NEXUS card for TSA for years. It stays in my wallet and is easier to pull out than my DL.
Also, a few states' regular driver's licenses are not and will never be Real ID. Washington has made a positive decision to not comply with Real ID requirements and our regular licenses already have "Federal Restrictions Apply" printed on them. Washington also issues Enhanced Driver's Licenses/State IDs which are Real ID compliant because of the documentation required to prove citizenship. I haven't bothered to get an EDL because I'll just keep using my NEXUS for TSA.