Slavery split the country not the Republican Party. The Chinese were not banned as they came in large numbers after the ACW. The Democratic Party was not in favor of Asian Immigration until the modern era. The ethnic cleansing of the Indians occured even before the US was a nation. Southern whites enthiasicaly participated in fighting Indians well before during and after the ACW. The Confedrate Army fought Indians and killed Indian civilians during the ACW and I have a thread in that. Southern whites were always in favor of racial superiority before during and well after the ACW.
Popular Sovereignty led to violence in Kansas but the thanks to John Brown for giving Abolitionists a spine the Abolitionists won.
Northerners had less than a 1% Black Population in 1860. All States added to the Union post 1860, were Northern States and had a less than 1% Black Population. Lincoln declared the Territories should be left for White Families. Lincoln was for Colonization. He rejected Abolition. All of this is why the Northern White Racist voted for him. Blacks emigrated in 1920s to the North, out of necessity. Yankee led Federal Government purposely rejected Black emigration. Even MA, the great Abolitionist State reject Black refugees during the War.
Chinese were Banned. Chinese exclusion act. Republicans called them Slaves. 2/3 of the women were sold into some type of Slavery. worked as prostitutes openly in lefty America. This went on until the 1920s in Slave California.
Sherman, Sheridan, Grant and Yellow Hair propagated a Race War during this Period against Native Americans. This went on until the next Century.
Republicans played on Northern Negrophobics fear of living with Blacks by rejecting Popular Sovereignty. There were less than 2 dozen Blacks in the Territories. 1 was too many for White Northerners. KS had no fear of Slavery. Brown like many Northerners wanted a Race War. They got one. Not in the South with Blacks. But one in the West with Northern led Federal Government. .
All of this leads to the Truth, that Northerners rejected all minorities of Color. Sad but true.