I checked with our Blender team and confirmed that Blender does not export blendshapes (shape keys) properly as .usd at the moment. The feature is not implemented yet, but they added that as one of the to-do features.
Also checked your files, and unfortunately none of them is ready for audio2face blendshape conversion. The one from .fbx → .usd is the closest, but it doesn’t have a skelAnimation prim, so can’t be used directly (we can fix this dependency in the future release).
In the meantime, if you have an access to Maya, you can probably use it to get .usd file that is usable in audio2face. I found your .fbx file can be loaded into Maya and the .usd from Maya is working in Audio2Face.
blender_andrew_test.usd (3.4 MB)
I’m attaching image and the .usd file from Maya.