The exact statements are not very close. The overall sentiment is as old as the hills. It certainly would not survive a motion to dismiss for copyright infringement. That is probably why they brought this (or represent it) as a "plagiarism" case. It sounds bad, and has a murky definition. In general, it is passing off someone's work as your own.
Well, Biden's speech did not use anything close to verbatim. At best he expressed the idea of the examples where a positive sentiment is better than its negative counterpart. That idea was not originated by the Canadian. The original work of the Canadian, at best, was the exact diction and wording used. Biden did not use that diction and wording, and thus was not passing off the Canadian's work.