First, a grenade is tossed near him at the Georgia event during the Russia trip. It did not explode though.
Second, a plane flies into restricted air space around Washington, DC and comes within 90 seconds of the White House. Reports show the small, slow plane entered restricted space at 11:28 a.m., helicopters were scrambled at 11:55, some 28 minutes later. Terrorism color code escalated from orange to red at 12:03 and returned to yellow at 12:11 p.m.
On 9/11, they sent Cheney to the basement, where he eventually ordered the military to shoot down a passenger jet. Today, they chased him off the property.
You are right "attempts". The real thing should be on the way. Even Americans themselves think so because the situation here in Baghdad is horrifying. The U.S. is indiscriminately killing everybody. The U.S. is also trying to drag Syria into the war. Bests!