We 'went into' Afghanistan well before that.

In 1979, the U.S. government began supporting and training anti-Soviet militias and warlords in Afghanistan, utilizing the Pakistani military and intelligence services to “funnel in money and aid to groups and institutions that the US viewed as favorable

The United States subsidized and protected local entities to pursue its goals in Afghanistan.
 The localities associated themselves with the American military in support of their own goals, but were reluctant to align themselves with their respective central government because the latter could not protect them. 

In the case of Iraq, moreover, the central government actively sought to diminish the influence of Sunni tribes and regions. 


Contrary to its own interests and intentions, the US, by supporting local tribes and militias, that  intervention has made it more difficult for Afghanistan and Iraq to consolidate their own central governments.