The FAA issued a NOTAM for LLBG (Tel Aviv Ben Gurion). That is a Notice to Airman. No, the FAA does not “forbid” destinations.
Quoting ...
The FAA prohibits all U.S. airlines from flying to and from Ben-Gurion International Airport “for a period of up to 24 hours.”
Another quote, another article ...
Following the action by the U.S. airlines, the Federal Aviation Administration prohibited U.S. airlines from flying to the Tel Aviv airport for 24 hours.
http://www.yorkdispatch.com/breaking/ci_26192520/delta-cancels-all-israel-flights-over-missile-fear
Another quote, another article ...
The Federal Aviation Administration on Tuesday blocked all U.S. carriers from flying to Israel’s main airport for 24 hours. The ban comes after a rocket landed about a mile from Tel Aviv’s Ben Gurion International Airport, the FAA said.
http://time.com/3019165/israel-delta-flights/