In the Election of 1856 it was bitterly divided over slavery. It won 23% of the popular vote and carried one state, Maryland, with eight electoral votes. The pro-slavery wing of the American Party remained strong on the local and state levels in a few southern states,
here is a North American review from 1924 that points out the links between the know-nothings and the KKK
Our national history shows phenomena of more o r less identical type appearing at recurrent intervals, and with astonishing regularity. This is especially the case with the present phenomenon known as the Klu Klux Klan. With the possible exception of masks, robes and other like paraphernalia, it is an almost complete replica of the old Know Nothing movement of the 'fifties of the last century. It professes the same objects, and uses nearly the same methods. Pessimistic citizens of the present day, who look upon our country as going fast and straight to destruction, should remember this fact and take courage.
Fur Shur more blacks were lynched by the KKK than Catholics by Protestants in America ~ by a factor of 100,000 I am sure!
The Know Nothings were a political party. The KKK sought to deprive blacks of all civil rights ~ and they enforced their ambitions with murder.
Now, let's turn our attention to Mexico ~ as I recall Sam Huston and other American Protestants were FORCED by Mexico to become Catholics in order to be allowed to settle Tejas!
This was way back there in the 1830/40 period.
Now there's a REAL "Know Nothing"/"Catholic" situation ~ but you will find, if you dig deep enough, that the Protestant dominated United States of America backed the Roman Catholic Republic of Texas to the hilt in their efforts to free themselves from the corrupt rule of Santa Anna!
This stuff was current news in those days and it could not help but fire the flames of bigotry and prejudice of the time.
I'd suggest you take up the greater part of the argument set forth by this author with the MEXICAN government ~ ask them for reparations for the FORCED CONVERSIONS!!!!