I think your only problem will be with Delta. The TSA/CBP (and, seemingly, their Canadian equivalents) only care about what's on one's passport.

I am a guy but changed my name when I got married (for numerous reasons not relevant here) to move my original last name to be a second middle name and added my new last name. I have not changed my passport because I am lazy and, more so, because I have some visas that I don't want to deal with getting reissued (e.g. China). So I have a passport with my original names (First, Middle, and Last) and a Driver's Licence (and other documents) with (First, Middle, old Last, new Last).

When you check in for an international flight you (or the agent) is prompted to enter the name "EXACTLY" as shown on the passport. I do and the check-in system never seems to care that the name I enter doesn't match the boarding pass. Sometimes when the are doing the document verification they notice but I just explain and they sometimes make some calls but I've never not been able to board.

I think the security checks / watchlist stuff is done either in real-time during check-in (i.e. the TSA "Do Not Fly") or while the flight is in the air. I don't think there is anything that is done before check-in.

ID matching to tickets is mostly an airline revenue protection action to prevent after-market ticket sales. It was the policy long before 9/11.