I have some assets that I created in ZBrush, rigged in Mixamo, and then textured in Substance Painter. First, I tried USD import as well as just the raw mesh. It looks really odd. When I load the FBX that I am attempting to import, it looks just fine. To note, the parts of the mesh having problems are single sided, non-closed areas. The closed portions of the mesh appear fine.
Below is the bottom of the leg. The tunic and pants are one-sided. The boots are solid and look fine.
Just to add, I brought the FBX into Blender and the mesh faces are all facing the proper way. Alternately, I did this for a building mesh and there were no issues.
I looked at the building and the problematic mesh. The building mesh had all the texture areas as separate materials. For the soldier mesh, I kept as one material and used vertex color to help painting. I did this to reduce the number of texture files. I tried to do this for another mesh and it seemed to be fine. I would rather find a solution for the import rather than having to re-export all the meshes, that would be a huge time sink.
It seems that with the USD import process, the material is getting imported rather wonky. I created the material manually with the texture files and it worked fine.