That'd be a decent argument except for...oh, I don't know.. the Iraq War

Bush has had a big impact on the course of American history. That's not necessarily true for all presidents, but it's true in this case.

He was also the product of a wider movement within conservatism. The skewed priorities of that conservative activism are also a big factor in America's current state. Bush himself may not have been the direct driver behind everything, but he serves as a good symbol for what's happened to America. You can track a lot of the current problems back to specific policies, and they are mostly Republican policies.