Enhancing State Energy Security Planning and Emergency Preparedness Act of 2021 This bill authorizes the Department of Energy (DOE) to provide financial assistance to states for the implementation, review, and revision of a state energy security plan that assesses the state's existing circumstances and proposes methods to strengthen the ability of the state to have a reliable, secure, and resilient energy infrastructure. A state energy security plan must contain specified content, including a risk assessment of energy infrastructure and cross-sector interdependencies and a risk mitigation approach to enhance reliability and end-use resilience. The plan must address potential hazards to each energy sector or system, including physical threats, and cybersecurity threats and vulnerabilities. Upon request of a state, DOE may provide information and technical assistance, and other assistance, in the development, implementation, or revision of a state energy security plan.