Re: Well, that was obvious.
Alternatively, they could have entered into dialogue with Kaspersky who have already mooted the idea of servers on US soil as a way forward. But they didn't, they just shut the door.
There's no reason why US samples could not be analysed in the US and only the developed signatures sent out globally.
When I look at the number of nation state malware examples Kaspersky has exposed or helped expose they look like the good guys to me. Can I entertain the notion that the US spooks are pissed at their work being exposed and are trying to weaken Kaspersky as a response? Yes I can.