Penny Plan to Enhance Infrastructure Act of 2021 This bill establishes discretionary spending limits for FY2022 and FY2023. Specifically, the bill establishes discretionary spending limits for defense and nondefense spending, establishes a separate discretionary spending limit for infrastructure spending, specifies the appropriations accounts and programs that are categorized as infrastructure spending for the purposes of the discretionary spending limits, and excludes infrastructure spending from the existing defense and nondefense categories of spending. (Under current law, the existing discretionary spending limits for defense and nondefense spending will expire at the end of FY2021, and there is no discretionary spending limit for infrastructure spending.)