Inside the US? Unlikely. This is physical hardware being shipped to the US, that sort of thing really lacks plausible deniability unlike rolling up phone records in foreign countries that happen to contain American tourist phone calls.

If these were found in a foreign country then maybe, but these would be far more likely to be some foreign intel service than the NSA.

Unless NSA is listening to the diplomats from other countries. Maybe this is a system to quietly force devices belonging to diplomats onto certain networks/nodes so they can be more easily intercepted. If someone wanted to simply shut down a network, a few basic white noise jammers could block frequencies far more easily/cheaply than a thousand sims.