There is no reason to assume that the Spellplague impacted other realities.
For several reasons
Crystal Spheres aren't part of The Realms campaign setting, they are added by Spelljammer.
First and foremost, understand that the concept of Crystal Spheres, and every other setting existing in a different one floating out in The Phlogiston is NOT core material to The Realms. It was added for the Spelljammer Campaign Setting as an optional way to tie all of the different settings together. In the FR wiki article linked in the question, note that the only source cited is the Concordance of Arcane Space...which is a Spelljammer Rulebook. The Planescape Campaign Setting offers an entirely different optional way to tie the settings together. This was explicitly done to let you play in multiple different settings with the same characters. It is, essentially, a hack applied on top of the Core settings.
The core settings (Forgotten Realms, Dragonlance, Greyhawk, Eberron, etc) all operate under the assumption that other settings either don't exist, or are sufficiently disconnected as to not matter. You never see a setting book explaining how this thing that happened in Eberron impacted these other things that happened in Faerun. They simply assume that the setting you are playing in is the only setting that matters.
Thus, outside of these two optional settings, travel between the two is impossible and Oerth and Faerun may not even exist relative to one another. (In a game played in Faerun, Oerth and 'Greyspace' may not exist at all). Based on that alone, each individual setting can be considered to be entirely cut off from one another, and cannot impact each other. Because without one of two optional campaign settings, no connection between them exists.
Nature of the Spellplague
The Spellplague was the result of a breakdown in the Weave of Magic caused by the murder of Mystra, goddess of magic. With no deity to manage the weave, it went rampant and caused a huge mess.
In Greyhawk, Boccob is the god of magic. In Krynn, it's Lunitari, Nuitari, and Solinari. In Eberron, there is no god of magic, magic is (theoretically) derived from Siberys, the golden ring around the planet (and dead progenitor dragon).
And, according to the Spelljammer rulebooks (concordance of Arcane Space p17-18) deities have no impact whatsoever on any crystal sphere they do not hold sway in. Unless they have a pool of worshipers there, or a powerful cleric who can make a connection, they can't interact with that sphere at all. The death of a god recognized in only one Sphere cannot impact another sphere.
The settings in D&D are extremely different. In terms of settings that go into significant detail on cosmology...The 'World Tree' cosmology was something unique to the Faerun setting.
Greyhawk was left intentionally vague in terms of cosmology. Krynn Cosmology looks like this. Eberron Cosmology looks like this. Old Faerun Cosmology (World Tree) looked like this, and the new version like this. See how different they are? There's no way these are the same planes in the same Astral Sea.
The simplest answer is that, according to the core settings, nothing that happens in one setting impacts anything that happens in another setting, because they are different settings. The fact that two additional settings (Spelljammer and Planescape) were invented to let you optionally glue them all together doesn't change the fact that they are entirely discrete settings with their own history and events that do not impact each other.