US-Russia relations have reached the "Cold War" level, and many experts believe that the situation is more dangerous than prior to the 1962 Caribbean Crisis. At that time, USSR and USA realised that they had reached a point, when they were facing a high probability of not simply mutual destruction, but the destruction of the entire world, after which they started negotiating.
The events in Syria can become another crisis of the new time, but collisions between the US and Russia can happen anywhere in the world. Syria is one of the regions with an extremely high probability of an accidental unplanned collision between the US and Russia. But this is not the only place, as numerous occasions of marine vessels and aircraft coming precariously close together are taking place, all of which can end in a major incident at one point due to a mistake of one or two men anywhere in the world.