[racional]

NATO was literally founded on the USSR's border ("Russia", as a top-level sovereign, did not exist), it had nothing to "expand up to", on either the Eastern or Western side.

Well that's not a fair assessment. It's technically true that NATO was founded on the USSR's borders via Norway. But there's not doubt that the expansion east of Germany, to include not just nearly all of Eastern Europe but a much more sensitive position directly on Russia's border (talking about the inclusion of the Baltics here) was hugely significant, and let's face it, also clearly a snub to Russia (despite their also wanting to join at one point; but that in no way mitigates the fact that NATO being expanded to their other countries was a move fundamentally aimed at Russia from the very start).

Not that this supports Russia's "because NATO" argument in any way; it's just pure garbage, of course. One can even argue that the expansion up to countries (such as the Baltics) that have been historically victims of Russian aggression is an intrinsically good thing. But there's no reason to attempt to water down the fact that the post-1990 expansion of NATO was hugely significant, and intrinsically meant as an anti-Russian manouevre (one can argue with perfectly good cause, in retrospect -- but there's no denying that import was there).

The fact that Norway and Russia shared a tiny border that most people don't even know about is entirely incidental to all of this.