> Russia would probably be silent if they had proof America did it, because they don't want WW3.

That doesn't make sense. Russia can use this as a propaganda tool without having to act on it. And it's not like that Russia didn't accuse USA from blowing it up - they did, just not very forcefully. It's strange, because they could have used it in e.g. Germany to split the society: "bad Americans want you to freeze, they blew up your gas pipelines".