It's been reported (by a number of sources) that the Russian Federation "warned" yesterday, 12 April 2018, that if any US missiles target sites in Syria, then the Russian assets would attempt to shut down the missiles and the launching sites would be targeted.
While this is generally reported as a warning, it is, in fact, worded as an ultimatum because it demands a reversal of policy. The President of the United States has stated that if it is found that the Syrian government was responsible for the chemical strike in Syria, then the US military action in Syria would be imminent.
I know that a number of inconsequential states have threatened the US after the Cold War ended. Some suffered dire consequences as results of such threats (Panama, for example). But what was the very last time a state actor gave the US an ultimatum backed by a military threat? Since I am counting the threat of war by Noriega as such an act, the "latest" ultimatum would have to be something after that. And, of course, it would have to be something before this ultimatum given by Russia.
I am asking to gauge what we should expect to be the US response (based on the previous credible ultimatums).