

This is not what you asked, but the only resource that immediate comes to mind is countercurrents’ list of every invasion the US has carried out compiled in 2013: https://www.countercurrents.org/polya050713.htm
I’m not sure if anyone’s compiled what you’re asking for. Of course the death toll of the US directly both contains events that pre-date NATO, and NATO contains countries other than the US.

As per usual, the answer is “depends on your threat model”. For a lot of sensitive communications, the centralised design and therefore ability to correlate metadata is a no-go. But if you’re just using it e.g. as a WhatsApp replacement to message your friends, it’s fine. It’s still the most polished and normie-friendly e2ee foss messenger.