An attack doesn’t necessarily mean Nuclear.
And anyway, he launched an ICBM the other day. NATO/America would’ve detected its launch. They wouldn’t have known it was only carrying a conventional bomb, rather than a nuclear warhead for which it was designed.
The initial reaction was to do nothing
Technically it wasn't an ICBM, it was an Intermediate Range Ballistic Missile and Russia informed the US of the launch. And it wasn't even carrying a conventional bomb - it was basically carrying fireworks!
It was pure sabre rattling from Putin, again. It's kind of worked I guess as a lot of people seem convinced we're now on the brink of nuclear war, but we are no closer.
It was a very expensive $50m launch of something they apparently have a very low stock of just to show his audience at home and admirers around the world that he's a big strong tough man.