Both of those are factors. There are other factors neither one of us knows about (even if you are in ocean transport - your competitors are doing things they are hiding from you until they happen). How they balance out is not something I know, someone in the field likely has a reasonably good idea despite not knowing everything.
OK, then the unavailability of containers is actually due to piracy in the middle east.
The US importing less, by itself, decreases the demand for containers.