I don't particularly frequent Before 1900 but a Japhy vignette is a Japhy vignette. I've always found tales of late stage pre-Civil War American politics to be both disturbing and entertaining and I'm not surprised that it's a setting for your style to thrive in. One thing I do find curious is the idea of anti-Catholicism as a unifying national force, I thought in this era it was something of a consensus anyway?
I'd be lying if I said I frequented Pre- much anymore myself but it seemed like a fun piece to write. Glad It was disturbing and entertaining.
It is rather surprising that the Know Nothings were able to enter the national stage in the late 1840's remain there up to the late 1850's but the thing is their Anti-Catholicism was both more fanatical --- most folks were Anti-Catholic but it wasn't a priority, it was with the "Native Americans" --- and served as a bit of a band aid to cover up the problems of slavery, slums and the complete lack of social reform. Add to that their proto-party was showing up just as the Whig party was collapsing and being replaced by an Anti-Slavery Party and they had a brief moment in the lead of up to 1856 to shine. Old Whigs, Middle Class Business-owners, the rural community and Southerners not keen on joining the Democrats all had a place to show up.
It wouldn't have been very good at unification Nationally, especially as immigration wasn't the big issue of the day and could never be, but I figure eight states in 1856 is the furthest they can do, I figured that by tossing them every state they were very close in in the South, which was pretty easy since they generally lagged by just a few thousand votes, and in the North gave them 1/3rd of the GOP vote in states where the GOP win was not dependent on the German vote, which is a hell of a lot, but you'll note it only swung two states, and the GOP was in its infancy anyway. Its enough to break the electoral college at least, which opens the door to someone more or less buying the race.
IOTL Fillmore was massively unpopular in 1856, and the middle class core of the Know-Nothing movement wasn't particularly keen on having a disgraced ex-Whig as their leader, much like how the Lib-Dems or NDP lost ground by offending their core base of support by going moderate, the same happened with these bigots. I figured their champion, tossing money around freely and buying up newspapers in a bid to purchase the White House probably invigorates that wing of the Party, instead of turning them into the dying Whigs/proto-Constiutional Unionists that they became.