That video is obviously based on many sweeping assumptions. And an underestimation of the kind of infrastructure and resources you need to build your own nukes as a country. Especially his thoughts on Germany sound like they were boshed together from reading subpar Wikipedia articles.
What is true is that the former Soviet satellite states in particular would be sitting ducks for the Russians if NATO retreats or even just weakens its stance on Article 5.
They could really be quite fucked if Trump wins the election.