Yes, it is possible for American airports to enforce even stricter security.
As soon as the leader of the notorious 9-11 attacks was killed, the department of Homeland Security and other federal groups have been/are on alert for threats from groups, such as Al-Qaeda, who may be seeking retaliation. In case the assassination of Osama sparks anti-American violence from his followers, the U.S. government recommends that Americans abroad stay in their homes/hotels and avoid demonstrations and other mass gatherings.
Within the country, TSA and airport employees have been told to be on extra-high alert for anything suspicious- such as hastily arranged attacks, since retaliatory groups would only have a few days to put an operation together. Coincidentally, the Department of Homeland Security recently (in January) released a new National Terrorism Advisory System. This system replaces the old color-coded threat levels with a plan under which the department issues specific alerts when it receives intelligence about threats. An elevated threat warns of a credible terrorist threat, whereas an imminent threat indicates a credible, specific, and impending terrorist threat. DHS has made it clear that they will only issue alerts when they have been given specific or credible information to convey to the public.
(Reference: Laura Williams )
