Keeping Everyone Safe and Securing Lives by Emergency Readiness Act or the KESSLER Act This bill directs the President to supplement disaster response plans to account for catastrophic incidents. Specifically, the President must supplement each Federal Interagency Operational Plan to include an annex containing a strategy to ensure the health, safety, and general welfare of the civilian population affected by catastrophic incidents by providing for the basic needs of the civilian population that is impacted by catastrophic incidents in the United States; coordinating response efforts with state and local governments, the private sector, and nonprofit relief organizations; promoting personal and local readiness and non-reliance on government relief during periods of heightened tension or after catastrophic incidents; and developing international partnerships with allied nations for the provision of relief services and goods. The strategy must include specified elements, including a description of actions the President will take to ensure the basic needs of the U.S. civilian population in a catastrophic incident are met. The Department of Homeland Security shall lead an exercise, as part of a national exercise program, to test and enhance the operationalization of the strategy. The President must provide recommendations for (1) actions that should be taken to prepare the United States to implement the strategy, increase readiness, and address preparedness gaps; and (2) additional authorities that should be considered to more effectively implement the strategy.