I have a hard time believing any type of "U.S. intelligence" coming out of the current administration, so color me skeptical at this point.
However, if ISIS did do this to Russia, they may find several things less to their liking in the future.
Let's put it this way; had this been a US plane, I have little doubt that Dear Leader would do less than nothing about it. Maybe a few words and a surgical strike or two to claim he hit back, but he's a wimp. And ISIS knows it.
.