Daesh (ISIL) military strategy shifted from defensive to offensive. It was Russia's involvement which spoiled the terrorists' game — in cooperation with Iran, it presented a united front from Central Asia through Shiite regions of Iraq to the Mediterranean.
These actions prevented Daesh from seizing Syria and stopped Turkey's attacks in the northern regions of the country. An absolutely local conflict eventually turned into a fight between Shiites and Sunnis, which put the United States on the spot. In Iraq Washington is on the Shiites' side fighting against Daesh Sunnis there, yet at the same time being the Sunni's ally in the whole Middle East (Saudi Arabia, UAE, Turkey) as well as in the war with the Shiites. The US was hoping that the Islamic caliphate would oust Assad, but it finds itself entering a war against the caliphate, asking its Arab allies to stop funding the terrorists.
Now Washington has to acknowledge the reality which it never wanted to acknowledge before. There is a revolutionary movement throughout the Islamic world, the aim of which is not only to get rid of the Western influence, but also to overthrow old elites, seize power, and take control over important energy resources. This is what jihadists did in Iraq, and what they are seeking in Libya now.
The US has realized that under whatever identity revolutionaries are fighting — whether Al-Qaeda, ISIS or Boko Haram — they all have the same goal: to establish a powerful Islamic state that will get rid of the influence of the Western world and their lifestyle as it happened 30 years ago in Iran under Khamenei; therefore the United States shouldn't support their aspiration for power.
That's why Washington involved the United Nations in the process of negotiations. In a few years the US may possibly realize, that the Islamized Europe with Turkey being part of it, might cease to be its faithful and obedient ally, and come to the conclusion that it needs to make peace with Russia. The reality is that when the Soviet Union collapsed in 1991, Russia became a Christian and European country able to build a powerful wall against Islamism.