C’mon. If the Russians wanted to nuke Europe with ballistic missile, all they’d have to do is take down the ABM radar in the Czech Republic. This they could do with a relatively short-range cruise missle attack. And if they didn’t want to be fancy about it, they could just ‘saturate’ the defenses with more missiles than the ABM system could shoot at. (there’s only a small number of interceptors).
The ABM system is oriented toward Iranian ballistic missiles. Putin’s bluster is more about driving a wedge between Poland & the US.
The relationship to the missile defense is clear. Putin who has voiced strong objections to missile defense in Europe is warning off all US allies (Poland et al) not to cooperate with the US since the US is not a reliable ally.