I believe that European leaders sense that inaction in the face of Russia does not have a positive outcome. However, action without buy-in from the US is also not worth contemplating, so acquiring that buy-in is of primary importance.
Recent reports of drone incursions into Poland and Romania have resulting in an NATO Article 4 invocation by Donald Tusk.
Presentation in the media is amplified compared to similar incidents such as the errant Ukrainian missile in Poland in 2022, during which Article 4 invocation was also discussed.
In a 2025 interview, Andrzej Duda, when asked if Zelenskyy had pressured him to say that the missile had been Russian, replied "you could say that".
Various casi belli are continuously laid at the feet of the Western public in the hopes that they percolate up to Donald Trump, although it does not seem likely that he will give his blessing to such action.
Perhaps soon, a casus belli will be found that makes war with Russia a moral imperative.