The United States has extradition treaties with the following countries:
So if these 13 Russians ever traveled to any of these countries, the local authorities would likely arrest them and send them to the United States for prosecution.
Edit: To everyone saying that Russia will just issue them fake passports with new identities, you are probably right. But when the US issues warrants for their arrest it will probably come with a photograph of their faces along with them. So unless these 13 Russians are willing to undergo facial reconstructive surgeries then they will have a much more difficult time traveling abroad. More than likely these 13 Russian agents got early retirement with a pension or are very wealthy on their own, so there will be no need for them to ever leave Russia.
I guess they can vacation in Crimea
Now that they've been outed their asset value is nonexistant in Russia friendly places too.
That is such a shame I hope they don’t resort to suicide by shooting themselves in the back of the head twice.