From the U.S. State Department:
The security environment remains complex in Israel and the West Bank, and U.S. citizens need to be aware of the continuing risks of travel to these areas, particularly to areas described in this Travel Warning, where there are heightened tensions and security risks. The Department of State strongly warns U.S. citizens against travel to the Gaza Strip. Furthermore, it cautions them that, with the exception of Jericho and Bethlehem, personal travel to the West Bank by U.S. government employees is prohibited. ...
Current information on travel and security in Israel, the West Bank, and the Gaza Strip may be obtained from the Department of State by calling 1-888-407-4747 within the United States and Canada, or, from overseas, 1-202-501-4444. For additional and more in-depth information about specific aspects of travel to these areas, travelers should consult the Country Specific Information for Israel, the West Bank and Gaza and the Worldwide Caution. Travelers transiting or visiting Jordan and Egypt during their trip to Israel should also consult their respective Travel Warnings, Travel Alerts and Country Specific Information, all of which are available on the Department of State's Consular Affairs website.
U.S. State Department Warning