The war which resulted in the separation of 13 colonies from the United Kingdom is often referred to as the American Revolution. However, as compared to revolutions like the French and Russian it wasn’t very revolutionary in the changes it brought to established power. It was a war of colonial independence. From its beginning it was a project of prosperous middle class white men. The structure of the nation which eventually emerged was very much geared to protecting and promoting their interests. The inhabitants of the new nation were excluded from the rights of full citizenship on the basis of race, gender and class. Most of the states established property requirements for white males to be able to vote. Mixed in with the declaration of the right to self government was the notion that in order for the republic to be sustainable, its citizens must be qualified and deserving of the right of self government.
The former colonists who set up the new government were a fairly homogeneous lot. The majority were of Anglo-Saxon heritage. There were people from the original Dutch settlement in New York. There were some Germans in Pennsylvania whose presence greatly irritated Benjamin Franklin. There were almost all of one flavor of protestanism or another. There were Catholics in Maryland, but they were of the polite English flavor. Not surprisingly, their notions about what characteristics determined the qualifications for self government came down to people who were just like them. As history unfolded over the next century it turned out that this was what the first congress had in mind when they used the term white.
Until 1840 the flow of immigration remained quite modest. The importation of new slaves was terminated in the constitution as of 1808. With the famine in Ireland and its attendant upheavals and the European revolutions of 1848, immigration began a long trend of acceleration. It brought great numbers of people who were not very similar to the founding WASPs in terms of religion, language and culture. They were eligible for admittance and naturalization because they superficially qualified as white. Between 1840 and 1924 there were movements of American nativism that questioned whether they were really white enough to qualify for the rights and responsibilities of citizens of the republic. There were a few occasions of lynchings of Italians and Jews. This process is tracked in considerable detail in Jacobson, Matthew Frye. 1998. Whiteness of a Different Color: European Immigrants and the Alchemy of Race.
With the California gold rush and the railroad building boom that followed there was a flow of immigrants from China into the west coast. The loudest voices demanding their exclusion came from Irish immigrants who were regularly condemned as unworthy by the WASP nativists. This resulted in the eventual passage by congress of the Chinese Exclusion Act of 1882. The Japanese came along a bit later. The effort by the nativists in terms of both groups was to block the immigrant generation from naturalization since they did not meet the white qualification. That could not be applied to their native born children. During WW II the Japanese, both aliens and citizens, were forceably interned in concentration camps. The west coast has it own rich history of racism.
The abolition of slavery was one of the issues that brought about the civil war. Five slave states remained in the union while 11 seceded. Slavery was legally abolished by the 13th amendment to the constitution. There were essentially superficial efforts to make changes in the relationships of southern society during the reconstruction era. When the presidential election of 1876 resulted in a deadlock between Hays and Tilden because of multiple contested elections, part of the resolution was to cut a deal with the south to let Hays, the Republican, have the election in return for withdrawing all of the remaining reconstruction controls. The former slaves were turned back to the hands of their masters and the era of Jim Crow was born.
That is a short and rather jaundiced overview of the great American melting pot. The pot has boiled over on many occasions, but the process has not been characterized by a gentle blending. The cutoff of most immigration from Europe in 1924 made it possible for the decedents of the immigrants whose whiteness had been questioned to begin to assimilate into the society. By the end of WW II most of them had attained the status of worthy citizens. That left those groups who had been excluded from the founding of the nation, the indigenous “Indians”, African Americans, Asian Americans mostly in the west, Mexican Americans in the southwest and Puerto Ricans on the east coast . All of them had been systematically and structurally excluded from the rights and privileges of citizenship.