Rob,

Per Gemini regarding Sierras,

Based on the information gathered, GMC Sierra trucks are assembled in several locations:

Fort Wayne Assembly Plant (Roanoke, Indiana, USA):
This plant produces various GMC Sierra models, including the 1500, 2500HD, and 3500HD.  
 
Silao, Mexico:
Some GMC Sierra 1500 models are also assembled in Silao, Mexico.
Flint, Michigan, USA:
This is where GMC sierra HD models are assembled.
Therefore, GMC Sierra assembly occurs in both the United States and Mexico.


I suspect that the lower trim levels are put together in Mexico.
I usually buy the lower trim levels.

https://soundcloud.com/sunset-poet-of-texas