AFAIK, none of those differences make any difference. The world of the current day Marvel movies is still essentially ours, despite the rewritten pasts and the added-in mutants.
I'm sorry, I don't understand what you mean by that. It strikes me as a self-contradictory sentence. If the past happened differently and there are things in the present that don't exist in our world, then it obviously
isn't our world, just one that resembles it to some extent.
The same things happened, even if it's now caused by mutants or had superheroes involved or whatever. The only time an alternate history has really made for a noticably different present is Watchmen.
That's really splitting hairs, and defining alternate history far, far too narrowly. There is no rule saying that alternate history can't have any events or individuals in common with real history. On the contrary, I daresay that a great deal of alternate history fiction is specifically
about alternate versions of people and events from real history.
I guess Trek is an alternate history with Henry Starling instead of Bill Gates, Voyager probes that went as far as VI, and load of differences like that, but it's still more or less our world. Time travel episodes to the relative present will always be a world recognizable as our own. If that makes any sense.
Again, though, that doesn't make it "our world," just something close to it.
And the more time passes, the more impossible it'll become to treat ST as anything other than an alternate history. We've already missed the Eugenics Wars, and even though Greg Cox's novel
The Rings of Time pushes Shaun Christopher's manned mission to Saturn back to 2020 (rather than 2009 as the
Star Trek Chronology conjectured), that's only 8 years away now, so it won't be long before it becomes impossible to pretend that's part of our future. And the Bell Riots are only 12 years in the future (though the social conditions posited in "Past Tense" are still disturbingly plausible), the
Charybdis (the
third attempt to explore beyond the Solar System) is only 25 years away, etc. Heck, some of us might even make it to 2063 to see warp drive and first contact
not happen. Even if you don't believe the point of irreversible transition of Trek from possible future to alternate history hasn't happened already, it's bound to happen in our lifetimes. Best to accept it now.