Europe will not jump in, they aren't stupid.
Europe is now in between building up their force, they know if they jump in that's gonna be bad. Europe want Ukraine to keep fighting the Russian, they have money and equipment, what they don't have is manpower and will to fight.
On the other hand, the chances of Putin to be able to reach Kyiv and threaten Ukraine is next to nothing, recently there were news that Russia is massing 50k troop near Kharkiv, that is all the Russian can spare at the moment, and 50k won't be enough to push into Sumy, let alone Kyiv
And finally, you are underestimating how popular Zelenskyy is, that guy is legit 80% favorability, if there is an election today, he is going to win a second term of 5 years, he will ALWAYS out tenure Trump, Trump is stupid because now, this attack basically is the Walter Cronkite moment in Vietnam war, this attack show you that Ukraine is far from done and this really is the best Russia can hope for, also this attack mostly devoid with US equipment (none of those drone and truck were from the US) which mean Trump lost the only connection to Ukraine, he can't dictate term anymore, Zelenskyy can just say no.
Said this before and I will say this again, this war will not stop even if US completely withdraw their support, this war is far, way too far from over, and it's going to take on a few years, by then Russia may or may not have taken the entire Donbas, probably not, but even if they did, they are going to looking at another one of these attack either in Donbas or in Russia itself and this is not going to be pretty for the Russian. Or you really believe they use this chances to just smuggle in 100 drones for this?? If they can smuggle those 5 container worth of drone, you have to wonder what else can they smuggle in.