Maintaining the President's Commitment to Our Nuclear Deterrent and National Security Act of 2012

Maintaining the President's Commitment to Our Nuclear Deterrent and National Security Act of 2012 - Expresses the sense of Congress that the United States is committed to: (1) ensuring the safety, security, reliability, and credibility of its nuclear forces; (2) proceeding with a robust stockpile stewardship program and maintaining and modernizing nuclear weapons production capabilities and capacities; (3) reinvigorating and sustaining its nuclear security laboratories and preserving their core nuclear weapons competencies; and (4) providing the resources needed to achieve these objectives.

Amends the National Defense Authorization Act for Fiscal Year 2012 to direct the President, upon determining that an appropriations Act fails to meet the resource levels needed to carry out the President's 10-year nuclear resources modernization plan, to submit to Congress a plan to remedy the shortfall, together with related information. Prohibits any reduction in the number of deployed nuclear warheads until 120 days after the President certifies that the identified shortfall has been addressed. Provides warhead reduction exceptions.

Prohibits, during FY2012-FY2021, any funds appropriated to the Department of Defense (DOD) from being used to carry out decisions made pursuant to the 2010 Nuclear Posture Review Implementation Study until the President certifies, among other things, inclusion in that year's budget of necessary resources to carry out such implementation, and that the resources have been provided in an appropriations Act.

Directs the President to annually certify to Congress whether plans to modernize or replace strategic delivery systems are fully resourced and being executed at planned levels.

Requires the President, during any year in which the President recommends to reduce by more than 1% the number of nuclear weapons in the active and inactive U.S. stockpiles, to certify to Congress whether such reduction will cause the number of such weapons to be fewer than the number of such weapons in the active and inactive stockpiles of the Russian Federation.

Prohibits, for FY2012 and thereafter, DOD or National Nuclear Security Administration (NNSA) funds from being used to carry out any reductions in nuclear forces unless the President includes in a report covering each country with nuclear weapons consideration of the expansion of the nuclear forces of any such country.

Requires the President, beginning with FY2013, to annually certify whether: (1) construction of both the Chemistry and Metallurgy Research Replacement building and the Uranium Processing Facility with be completed by no later than 2021, and (2) both facilities will be fully operational by no later than 2024.

Prohibits the use of DOD or NNSA funds for FY2012 or thereafter to reduce to only one the number of nuclear warheads contained on an intercontinental ballistic missile (ICBM) unless the President certifies that the Russian Federation and China are both carrying out a similar reduction. Provides an exception.

Expresses U.S. policy on the reduction of Russian nonstrategic nuclear weapons and the U.S. extended deterrence commitment to Europe. Provides a limitation, for FY2012 and thereafter, on the reduction, consolidation, or withdrawal of U.S. nuclear forces based in Europe.