From the U. S. State Department:
The Department of State warns U.S. citizens against travel to Afghanistan. The security threat to all U.S. citizens in Afghanistan remains critical. ...
Current information on travel and security in Afghanistan may be obtained from the Department of State by calling 1-888-407-4747 toll free in the United States and Canada or, for callers outside the United States and Canada, a regular toll line at 1-202-501-4444. These numbers are available from 8:00 a.m. to 8:00 p.m. Eastern Time, Monday through Friday (except U.S. federal holidays). For further information, please consult the Country Specific Information for Afghanistan and the current Worldwide Caution, which are available on the Bureau of Consular Affairs Internet website. You can also stay up to date by bookmarking our Bureau of Consular Affairs website, which also contains current Travel Warnings and Travel Alerts.
U.S. State Department Warning