You're saying if the CIA does so in Russia, it would lead to military confrontation?
Ed Snowden is a card to play for Russia but a quite small one.
Actually, the biggest risk he is facing is the same as Julian Assange. At some point, a change in policy in Russia (eg getting something back in return from the US) can lead to him being extradited to the U.S.
As for the U.S, I think it's not a big deal as well. His damage is done. All the incentive the U.S has in this case is to make example of him.
There is little political incentive for politicians to follow. Maybe some PR for the president who manages to get him back, but aside from that, Ed Snowden is not a big incentive for anyone at this point. No way anyone is going to war for him.
Snowden is a card with an expiration date. Sooner or later Russia will try to use it to get something back.
[1]https://www-m.cnn.com/2019/09/09/politics/russia-us-spy-extr...
USA has plenty of whistleblower examples anyway. We've tortured Chelsea Manning for years. Others who have been punished, to varying degrees, include Bill Binney, Reality Winner, and John Kiriakou. Presumably there are others of whom we're not aware. These people have done really small things to rouse the ire of the TLAs. How could they punish Snowden in a proportional fashion, anyway?