Nothing new under the sun. Proxy wars are an old thing, and they're still a valid strategy because they are very good for the economy, this should not surprise anyone. The Ferengi Rule of Acquisition #34 wasn't made up, like most things in Star Trek it's not so much fiction, but a distorted parody of real 20th century history and racial clichés.
In every proxy war, the larger nations support one or the other side (sometimes both), always with most honorable justifications, and keep the conflict going for years, or decades. After all, someone has to buy the weapons you manufacture, and as long as war stays in some far-away country that most people have trouble finding on the map, it's all fine. Spain, China, Korea, Vietnam, Angola, Sudan, Ethiopia, Nicaragua, Afghanistan... did I forget an important one?
So... the question of questions... will this turn Russia and USA against each other, will it escalate to a huge war? Of course not. They have an interest in keeping this conflict going, but they have no interest whatsoever in a conflict between the superpowers. They're not insane, you know. This is about business, not about total extermination in a global war. Sure, they'll do their propaganda show, but... whatever.
You need to have an enemy and an immediate threat after all, or the whole thing doesn't make sense. How do you govern a country when there are no present and immediate threats, and your citizens are not afraid of someone? How do you make them comply with the idea of your war (which is good for business)? How do you make them comply with their civil rights being violated every day? How do you convince a random young man to go to a far-away country and die in a trench with his guts hanging out of his belly, if there is no enemy that needs to be destroyed? Sure enough, hate and fear are most valuable properties, and you need to feed them regularly. So yeah... propaganda will go on, of course. But that's just... The Show.
You never asked yourself how some random arab guy who can barely write his name managed to capture an airplane and crash it... not just in the world trade center, but right into the Pentagon? Seriously? Right into the most secured building in the country, flying through the probably most paranoia controlled airspace in the world with F18s in the air at all times? Come on, you never wondered how that could have happened? Enemy, babe... you need an enemy. And you need fear.
It's not even certain who repeatedly used chemical weapons in Syria or bombed a chemical weapon factory or whatever. Assad? Maybe. Some IS guy? Maybe. But it might very well have been US military or Russian military, too. What do we know about it? Nothing. Only what we're being told. You cannot even be sure that the so-called IS isn't in reality the CIA (it's not like they hadn't done similar before, think e.g. Operation Ajax).