Protecting Critical Infrastructure Act of 2021 This bill increases federal criminal penalties for computer fraud and abuse offenses that involve critical infrastructure. The term critical infrastructure means systems and assets, physical or virtual, so vital to the United States that the incapacity or destruction of such systems and assets would have a debilitating impact on security, national economic security, national public health and safety, or any combination of those matters. Specifically, the bill imposes a fine, a mandatory minimum prison term of 30 years, or both for a computer fraud or abuse offense that involves critical infrastructure. Additionally, the bill directs the President to impose asset- and visa-blocking sanctions on foreign individuals and entities that access or attempt to access critical infrastructure.