LET'S JUST UNPACK BRIEFLY WHAT DK ALLUDES TO IN PASSING HERE

"...Given that the 1924 act was followed 70 years later by the commission's recognition, one could hypothesize that a periodic reaction against immigrants is indeed part of our 80-year historical cycle.  The same thing was also happening in the 1850s, but then, slavery, rather than immigration, became the focus of those concerned with the rights of free American workers...." DK, The missed chance on immigration

Those most concerned with the rights of free American workers were the Northern racist Republicans, who had been whipped into a frenzy of fear and anger by the likes of Lincoln who claimed falsely that the South intended to nationalize slavery, thus driving white labor from the market in the North as well as in the South. Lincoln had made this part of his political campaigns from the early 1850s or before.

He first rammed the negroes up Northern white voters' asses, then rammed them up white Southerners with Civil War Emancipation. 

Lincoln was the most adroit of all slave drivers America ever produced.

Meanwhile, as I have pointed out here before, Lincoln got passed, during the Civil War, the most expansive and racist immigration law America has ever had, promoting massive white only immigration to replace the negroes he nevertheless was freeing rather than transporting.

Wikipedia: An Act to Encourage Immigration