Edelbrock, in LA area, Torrance Ca.
Holley, Bowling Green Kentucky,
like 10+ or more brands under that label now
Quickfuel, Bowling Green Kentucky
QA1, Lakeville Minnesota
Strange Engineering, Morton Grove Il.
Crane, Daytona Beach Fla.
Lunati, Olive Branch Ms.
Chris Alston Chassisworks, Sacramento Ca.
Moroso/Competition Engineering, Guilford Ct.
Aeromotive Inc., Overland Park Ks.
above is just a fraction of the many "parts" or specialty supply businesses
it's not a very short list, like said by someone, 10's of thousands
especially the smaller Mom & pop shops & distributors
it's extensive, you just need to look for it/them
it may take more time but you can find Made in USA products easily
especially the SEMA affiliated stuff