From the U.S. State Department:

The Department of State strongly urges that U.S. citizens refrain from all travel to the Gaza Strip. This recommendation applies to all U.S. citizens. U.S. citizens should be aware that as a consequence of a longstanding prohibition on travel by U.S. citizen employees of the U.S. Government into the Gaza Strip, the ability of consular staff to offer timely assistance to U.S. citizens there is extremely limited, including the provision of routine consular services. ...

The Department of State urges U.S. citizens to exercise caution when traveling to the West Bank. Palestinian Authority (PA) security forces are now deployed in all major cities and other limited areas within the West Bank. As a result, violence in recent years has decreased markedly throughout the West Bank. Nonetheless, demonstrations and violent incidents can occur without warning.

U.S. State Department Warning