The Obama NPR interview explicitly talked about this. (with some pretty important implicit parts)

It was basically that there has been an obviously unwritten understanding among major powers that they will try to spy on each other but will generally keep out of their internal power transitions. (implying that lesser countries are up for grabs) It was something I found shockingly frank to just put it out there that way.

So yeah, in that sense it really is a big deal. This sort of thing has been considered in bad form among equals, basically.

So yeah, US and Russians have aided groups (and continue to aid groups) in other countries. But that's where the whole concept of spheres of influence comes into play. It's not necessarily nefarious, think of it like a city. See how the entire state of Illinois pretty much revolves around Chicago. Yeah there's some resentment about it, but at the end of the day it's because it's the economic driver. The same thing happens internationally with geopolitics.