classic American made carb brands, were there fewer than I thought, or just not many got contracts to be factory equipment on production cars?

Holley, Carter, Edelbrock, Rochester, Autolite, Stromberg, and Winfield are the ones that I can name by memory

Carter made the 1st 4 barrel, in 1952 for a Buick - and produced Rochesters and Webers

Autolite would place a Ford tag on carburetors purchased from Carter, Holley, and Rochester; so many carburetors with a Motorcraft tag actually were made by other companies

Carters foundry was so contaminated with PCBs it was turned into a EPA Superfund site a year later. 

https://en.wikipedia.org/wiki/Carter_Carburetor

The Carb Shop has an online database to share the carbs and information that they had gathered in 5 decades of operation

Autolite, Carter, Detroit, Ensign, Holley, Kingston, Linkert, Marvel, Motorcraft, Rayfield, Rochester, Schebler, Stromberg, Tillotson, Winfield, Zenith

https://www.thecarburetorshop.com/Carbshop_virtual_museum.htm

The Sunderman Carburetor Company offered a replacement carb for Model Ts, which had a trap-door similar to the design of some early mouse-traps. While early advertisements do not show the "Mouse Trap" data plate, at some time the name was given to this carburetor.