National Debt is National Security Act This bill establishes limits on the portion of the national debt that may be held by foreign governments, entities, and individuals. Specifically, the portion of the national debt that is cumulatively held by foreign governments, entities organized or incorporated under the laws of a foreign country, and citizens of foreign countries may not exceed one-fourth of the national debt. In addition, the portion of the national debt that is cumulatively held by the government of a single foreign country, entities organized or incorporated under the laws of the country, and citizens of the country may not exceed 5% of the national debt. The bill allows the President to waive these limits if the President determines and reports to Congress that an important national interest requires the waiver.