Russian President Vladimir Putin ordered several Military exercises near the border of Ukraine in response to President Barack Obama's sanctions passed to the Congress, It's a clear warning to President Obama to back off the situation in Ukraine because Russia never interfered any U.S. Military activity in other countries like Iraq, Afghanistan, Libya, and a lot more.
Yes, I think that Russia was warning the U.S. because Putin likes to show off how powerful Russia is. It gives him a kick to show off to his people because he knows that the current US administration will not do anything about it. Like Obama said to Putin, he would have more flexibility after the election, and that's what he's done.
The Russian fighter jet that buzzed closely by a U.S. Air Force aircraft that was on a routine mission wanted to know how the U.S. was going to respond to any aggressive act. Russia does not want to become involved in any aggression with the U.S., but will get by with what the U.S. allows.
I believe that President Putin was sending a message to President Obama that he is watching very closely. I think he is very power hungry and was upset by the sanctions that President Obama set again him and his other high officials after he set Russian troops into Ukraine. I think this needs to open communication with Russia and the United States.
For a serious warning or threat, Russia would do something more obvious and overt than something like this. Something like this is either a misunderstanding or some simple posturing between the two groups. If it had been a warning, then something more serious would have happened already between the countries.