Final assembly of these vehicles is done in Canada, Mexico and the USA.
Regardless of the final assembly point, the powertrain (engine and transmission) is likely to have been built at the GM plant in Silao, Mexico.
https://www.motorbiscuit.com/1-full-size-american-pickup-tru...
Bottom line --- the typical consumer really has no idea what he is getting when he buys "American". The people selling it typically don't really know either but they will gladly tell you whatever they think you want to hear.