The Soviet defeat in Afghanistan had a substantial role in ending the USSR in that it shook the confidence of the leadership and discredited the regime with the Soviet public. And after Afghanistan proved that the Soviet conscript army could not subdue tribesmen living in mud huts, that same army became a doubtful instrument to enforce Soviet rule in occupied Eastern Europe. An empire may long survive even though hated and thought to have internal weaknesses, but its end is in sight when its weakness is revealed.
While Europe and the US have far more to lose, Islam is a more immediate threat to Russia. And while Putin may be the big man in the Kremlin for the rest of his life, he is not immortal. Worse, the Putin regime has no solution against Islamic aggression except to ally with pliable Muslim thugs and dictators; and as Putin's vitality declines due to age, a Brezhnev style era of corrupt stagnation seems inevitable.
Meanwhile, the US and the West are showing signs of rallying against Islamic terrorism. The American public especially seems to be nearing the limit of its acceptance of Muslim aggressiveness. And, with the illusion of Muslim democracy having worn thin, sterner measures seem likely to be restoted to.
Perception is not reality. The USSR and the eastern bloc ended because their system did not work and it was already on its last legs. It was already being predicted it would end in the 70s. If we had done zero in Afghanistan the USSR would have fallen in the exact same way - maybe even sooner because a war in Afghanistan kept the old regime from admitting defeat sooner.
Alternate history scenario: We would have been better off if Afghanistan was given to the USSR (it was already ruled by a home grown commie regime that was having trouble with the rurals) in return for allowing the USA a free hand in Iran to invade it and to return the Shah's regime. The American people were all set to go to war over the hostages.