Asking that question from the hindsight is doubly unfair. First hindsight is always 20/20, so we are comparing what we know now to what was known at the time the decision was made. A better question is, when the decision to invade was made, was it made on sound information and judgment, or in the Bush-style, based on poor judgment and fabricated facts.
Second, and more importantly - we do not know what an alternative would have been, had the Soviet not intervene. The tacit assumption is that Osama, Taliban and Islamic terrorism would not have emerged, but this only a conjecture. Perhaps it would not, or perhaps it would, and in a more vicious form, but we have no way of knowing.
This is yet another example of the fallacy of attribution of causality to the single most salient factor (in this case, Soviet intervention), which I mentioned in my earlier postings.
Wojtek