Railworks America

I can't figure out, where this stuff came from in the first place?

I have some generic US freight cars , under Kuju\RailsimulatorUS directory
They don't belong to any route pack or add-on.
I got the game in 2012 with some pre-installed routes (Cajon Pass and Horseshoe Curve and some European stuff),
but I think these cars already was there?
Did RSC/DTG stop to distribute these ones after some period? Kuju is no longer exist as owner of the product though
Is there a chance that users of TS2014 and 2015 don't have them?

also, when I wiped out assets directory and reinstalled everything from Steam, these cars reappeared too

the cars in that folder are: double stacks, autoracks, boxcars, reefers, some hoppers - all of generic appearance (no reporting marks)

examples:
C:\Program Files (x86)\Steam\steamapps\common\RailWorks\Assets\Kuju\RailSimulatorUS\RailVehicles\Freight\AutoRackCar\Def2\Wagon\auto_rack_car_Def2.bin
C:\Program Files (x86)\Steam\steamapps\common\RailWorks\Assets\Kuju\RailSimulatorUS\RailVehicles\Freight\AutoRackCar\Def2\Wagon\auto_rack_car_Def2.bin
C:\Program Files (x86)\Steam\steamapps\common\RailWorks\Assets\Kuju\RailSimulatorUS\RailVehicles\Freight\RefridgeratorCar\Def2\wagon\refrigerator_car_Def2.bin
C:\Program Files (x86)\Steam\steamapps\common\RailWorks\Assets\Kuju\RailSimulatorUS\RailVehicles\Freight\BoxCar\Def2\Wagon\box_car_Def2.bin

Please check if you have these cars, I used them in some scenarios but I can't detect what is dependency package for them

Yeah those cars are what us old timers call the "default" rolling stock. They are now part of the US Asset DLC package. If you had 2012 or earlier you have them. Maybe even 2013 had them.

Yeah Bob"s right. They used them for Cajon Pass and Castle Rock originally. It also includes some U.P. and BNSF ES44s and SD40-2s. Those are what some older reskins and repaints are referring to.
I think if a person buys Cajon Pass they also get those assets. That's usually cheaper than the asset pack and gives a person another route to drive.