Moreover, as I said, the U.S. knows Russia is not about to conduct a surprise bombing raid on them, so does Russia know the same of the U.S. - They both have nuclear weapons and doing so would be catastrophic for both sides. Iran on the other hand expects a U.S. bombing raid any moment and in fact Trump just admitted one was ready to go ahead, so it's a bit different.
In fact, I suspect the U.S. knows all this and provoking a reaction from the Iranians to support further action from the U.S. was precisely the goal of this drone.