As an intelligence source it would be invaluable, see their IP addresses, locations, who they're talking too, what they're saying, their social graphs, what els

As an intelligence source it would be invaluable, see their IP addresses, locations, who they're talking too, what they're saying, their social graphs, what else is on their devices, etc. It's probably better to keep all that under American control rather than just 'banning' them for optics. Although as we've just seen that intelligence is almost certainly not acted on or taken notice of.