What is conducted to protect the US from external threats as directed by the President?

The correct choice is Homeland Defense, which refers to the actions taken to protect the United States from external threats, encompassing a wide range of military and security measures. This concept includes the prevention of attacks against the nation, protection of critical infrastructure, and the deterrence of adversaries. Homeland Defense is directly governed by presidential directives and involves coordination between various agencies and military branches to ensure the safety and security of the nation from external dangers.

Other options, while related to national security, do not specifically encapsulate the comprehensive governmental and military response to external threats as designated by the President. For instance, 'National Security Framework' describes the broader principles and policies shaping the nation’s security strategy but lacks the focus on protective measures against external attacks. Similarly, 'Homeland Homefront' and 'Shields of America' do not have established definitions or frameworks recognized in national defense strategies, limiting their applicability in the context of direct presidential directives regarding national defense.