GWB did let in folks from Afghanistan, so yes, he is partially to blame.
GWB did the right thing in going to war in the ME. He developed Infrastructure in Iraq, which we desperately needed, especially for Intel. Then what happened? Day after day, he was attacked by media and democrats, constantly 24/7, making it impossible to wage a quick and successful war. Then ask, what happened next? Obama GAVE IT ALL BACK to the terrorists. They were far more concerned about underwear on prisoners heads in Abu Graib, GITMO and Valere Plame being outed, then keeping America safe.