Russia is not amassing troops on on its south-western border.
what was presented as Russian troops ready to invade Ukraine was a group near the border with Belarus when Poland moved 20% of its army to Belorussian border "to repel 2000 migrants", and it was obvious Poland could attack Belarus.
According to Americans themselves those troops were 400 km from Ukraine, it is approximately the same distance as from Moscow to Ukrainian border

it was a fake accusation, a fake story, aimed to prevent Russian response to Ukrainian aggression against Donbass.
Don't dare to respond or you will be accused of invading Ukraine, sort of...
But this Putin's ultimatum was intended to be rejected. Everybody understands that the US is inadequate and rejects reality, not ready to acknowledge decline of the US.
So, I presume we're going to see American rejection and then Putin will roll out his promised "military and techno-military measures".
I am looking forward to seing what he meant