What do you mean by you cannot enable collision?
By default you will not have collision set up for the simple collision, you will have to generate it in the static mesh editor.
In 5.4, support for collision was implemented, so UE can read collision from the USD file. This support was added through the implementation of the following schemas:
- UsdPhysicsCollisionApi: to specify meshes/prims as colliders
- UsdPhysicsMeshCollisionApi: to specify collision shapes on meshes/prims