At least as long as the CIA operatives are not crazy enough to run an armed operation in Moscow.
But yeah, I seriously doubt they'd kill anyone unless they needed to.
Moreover, even if the US managed to grab him, it'd be easier to manufacture a bogus story explaining how he suddenly ended up in custody. After that, he'd just be sent off to ADX Florence for life.
They could likely assassinate him in most places, although in NK/RU/CN/IR it would likely involve a lot of collateral damage, although probably not global thermonuclear war.
Umm, no. That's not quite how things work.
That ruffled the feathers until a few years later when it was all swept under the carpet.
Now the disagreement is over Ukraine and Syria. So Russia is in the bad books again for the killing
In Russia? Spetsnaz would eat them alive. Maybe Mossad could pull it off but no way the CIA.
And what has anybody ever done about it? Maybe sent out a few strongly worded memos, if anything at all.
The fact that it might ruffle a few feathers diplomatically is hardly something the CIA considers when they handle operations like the one they're describing. Also, if they did grab him, trust me, he wouldn't be heard from again. Considering Snowden has an army of governments after him, it would be easy for the CIA to run a disinformation campaign to keep people guessing who really kidnapped him.
It would be easy for the CIA to rotate him between several of their "black sites" around the world and basically let him wither and die in one these miserable places.