I think the U.S.S.R. was destroyed by the West, first by military attacks during the Revolution and Civil War, then by subversion, then by the attack of Adolf Hitler, then by the Cold War, when the West encircled the U.S.S.R. with military bases, threatened it with nuclear anihilation and forced it to spend for self-defence the funds that should have gone into reconstruction of the appalling devastation of WWII.
I believe the Soviet people could have been mobilized to continue the struggle against fascism's successors, but the Soviet leadership took some wrong turns, opting for the easy way out once the immediate danger of Nazi Germany was demolished.
Reagan's role in all of this was minimal. He continued policies that had been developed by others - - bleed the Russians. Star Wars was a part of it, Afghanistan was a part of it. Sure, the Afghan War was a socialist mistake, but the U.S.S.R. was asked to come to the rescue of a sister socialist government, fighting off an attack from 19th-Century warlords and they fulfilled their socialist duty of solidarity. Maybe the mistake was not getting out sooner (which would only have encouraged the fascists of Eastern Europe to rise up against the Red Army) or maybe they should have assessed the situation better and seen where the Afghan Communist Party was going wrong and failing to mobilize the population against the warlords. Maybe if the warlord allegiances were tribal, this should have resulted in a shake-up of CP leadership cadres. I don't know exactly where they fucked up, but it's pretty clear in the result that fuck up they did.
I tend to agree with XO here - - Reagan was a figurehead, an empty suit. A decades-old policy (bleed 'em) obviously has to adapt to changing times and new opportunities and at most that's what Reagan allowed to happen. Others saw the opportunities, crafted the basic policy through its new adaptations (war in Afghanistan, Star Wars) and Reagan was savvy enough to stay out of their way.
I wonder how many Americans see the tragedy in the fall of the U.S.S.R. It's certainly no secret to the Russian people, whose standard of living, quality of life and even life expectancy have plummeted dramatically since the fall of communism.