When the Russians "botch" a job they do so with a reason. If you want to quietly disappear someone you don't do it with chemical weapons or radioactive material. You use such things when you want people to know about it, when the goal is remind everyone exactly who they are dealing with. Dig into things and you will find lots of Russian agitators disappearing under suspicious circumstances. They know how to do things properly when they want to. They don't dress up in the dead man's clothes and do a little dance for the cameras.

Whether any killings have happened on US soil is an open question. But, without mentioning the T word, I think not much would happen. Both chemical and a nuclear weapon were deployed in Britain ... and Russian operatives still move in and out of the UK freely. Russian money still invests in London real estate. I don't see why anything different would happen in the US.