Russia and US can't even share Syria, Turkey is a much greater and "significant" country. Even Trumps Russian love has its limits.
Russia supports Assad, the US opposes most actors, but most obviously ISIS. In this case Erdogan has explicitly made enemies of both superpowers. It would be as if Assad shot down a Russian plane and then turned around and told America he'd have Russian missiles, and then turned around and told the EU to expect more refugees. You can bet Russia and the US would cooperate in that case.
Turkey is not some random ass tiny country you can invade, such an attempt would be either result in a failure or major losses. It'd be political suicide for the adminstration attempting it.
This is literally what was said about Iraq in 2003. Iraq had at the time one of the top 10 largest militaries in the world. The largest by share of population.
Not only did the invasion succeed, but the administration that did so in the second gulf war was reelected by a far wider margin than their first election. The political fallout was in fact, only later felt by subsequent administrations that would hold the blame (eg. "Obama is a warmonger" as he dealt with the aftermath).
It'd result in a massive refugee crisis, greater than the Syrian one. I'm sure EU would be delighted.
Part of the conditions of peace could be that the Turkish government foot the bill for re-locations, while a joint Russian-Kurdish-Nato force maintains a safe zone.
Good luck displacing 15+ million muslims in Istanbul.
Who said anything about that.