It is not, because a random user is not able to use it.
A thing only affects a monopoly when it is a choice a consumer can make.
You could say that iphone is an anti-monopoly option vs android, but not that Safari is an anti-monopoly option vs Chrome.
Then on top of that, even for users that do happen to "live in Canada"(1) already, Safari isn't a choice, it's the only allowed option, and full octane firefox is also not available as a choice. (firfox as a front-end to safari is essentially meaningless)
(1) saying "you can use Safari, because you can switch to iphone" is the same as saying you can have something, just move to Canada", ie, invalid and likely disingenuous, because likely the speaker understood that perfectly well.
So, yeah "let's be real" indeed. There is no way to paint Safari as any sort of anti-monopoly.