This isn't quite what you are looking for, but no discussion of post-war American race relations is complete without President Truman's Executive Order 9981.

The full text of the executive order reads as follows:

EXECUTIVE ORDER 9981 Establishing the President's Committee on Equality of Treatment and Opportunity In the Armed Forces.

WHEREAS it is essential that there be maintained in the armed services of the United States the highest standards of democracy, with equality of treatment and opportunity for all those who serve in our country's defense:

NOW THEREFORE, by virtue of the authority vested in me as President of the United States, by the Constitution and the statutes of the United States, and as Commander in Chief of the armed services, it is hereby ordered as follows:

1. It is hereby declared to be the policy of the President that there shall be equality of treatment and opportunity for all persons in the armed services without regard to race, color, religion or national origin. This policy shall be put into effect as rapidly as possible, having due regard to the time required to effectuate any necessary changes without impairing efficiency or morale.

2. There shall be created in the National Military Establishment an advisory committee to be known as the President's Committee on Equality of Treatment and Opportunity in the Armed Services, which shall be composed of seven members to be designated by the President.

3. The Committee is authorized on behalf of the President to examine into the rules, procedures and practices of the Armed Services in order to determine in what respect such rules, procedures and practices may be altered or improved with a view to carrying out the policy of this order. The Committee shall confer and advise the Secretary of Defense, the Secretary of the Army, the Secretary of the Navy, and the Secretary of the Air Force, and shall make such recommendations to the President and to said Secretaries as in the judgment of the Committee will effectuate the policy hereof.

4. All executive departments and agencies of the Federal Government are authorized and directed to cooperate with the Committee in its work, and to furnish the Committee such information or the services of such persons as the Committee may require in the performance of its duties.

5. When requested by the Committee to do so, persons in the armed services or in any of the executive departments and agencies of the Federal Government shall testify before the Committee and shall make available for use of the Committee such documents and other information as the Committee may require.

6. The Committee shall continue to exist until such time as the President shall terminate its existence by Executive order.

Harry Truman

The White House July 26, 1948

Why is this important? Because it created the precedent for much of the later civil right and equal rights laws that would be enatcted in the United States later on in the 1960s and 1970s. Also because after the experience with racial hierarchy in Nazi Europe, the government and society of the United States began to become increasingly uncomfortable with the types of racially-based class systems that had prevailed in the United States for much of the 19th and 20th centuries.

I know that this isn't what you were looking for exactly, and I'm not sure how relevant it will be to a Netherlandish audience, but it's a short primary document that is well-known in the United States as one of the first official efforts of the federal government to enforce anti-discrimination measures. Notice that it does not just mention "race" (an exceedingly vague concenpt, even then), but also "color, religion, and national origin"!