The world has entered the Second Cold War with many Pro-Russian vs. Western conflicts began to pop up around the world. You have the Syrian Civil War that Russia is blocking the West from stepping in. You also have the Ukranian Crisis in where the Russia has Seized Crimea from Ukraine.
There is plenty of tension building up and up and up. The tension of the world will cause a global war worse than what our ancestors saw. I never thought I'd say something like this but picture the world the way Activision and Infinity Ward has depicted the world. Maybe I'm wrong about this, but I know I'm not wrong about this: something is going to give
With the crisis going on in the Ukraine, the situation with Crimea, and other things surrounding it, we are edging closer to another Cold War. Are we in one yet? I don't believe we are. I do believe however, that a Cold War is bound to happen if these kind of events keep happening.
Our governments just realized the "hey look over there" tactic is a better method of control than pure MAD fear.
Now they use a divisive, partisan media to gridlock the nation and teach the controversy, rather than focus on solutions to problems, they just scream hyperbole and cast blame indiscriminately.
So Yes, we are in crisis, Yes we are in a cold war, but it never ended to begin with, it simply "cooled".
Let's start from the beginning, shall we?
 Crimean Conflict: The conflict between the Ukraine and Russia over the area of 'Crimea' started a conflict between Russia and the United States as well. This led to not only diplomatic issues, but also militaristic issues. Russia moved its troops into Crimea and Ukraine claiming they were only "protecting the land".
 Ukrainian Revolution is another issue that caused international conflict. When the government gave in after losing several officials to protests and acts of violent civil disobedience, Neo-Nazis took over. The USA didn't like this, but still was trying to help stabilise Ukraine and also fend off Russia.
 Iran Threats also were an issue as time progressed. The Iranian government threatening constantly to bomb and/or invade Israel increased. Of course, with the USA not only being allies with Israel, but the police of the world, they had to get involved.
 War In Middle East is still occurring and it is painful to know that this war has lasted so long. Efforts to make peace are not known of, but may be happening. Middle Eastern nations still hate America and Russia is hating America more and more.
 Cold War is not incoming nor is it occurring. However, since the beginning of the Crimean Conflict, I have feared the evolution of World War III slowly over time. I believe that what we are looking at is a Third World War.
No, the US is not entering a second Cold War. Putin is testing us, sure. But the jet incident could easily have been a misunderstanding, and Russia doesn't have near the same military power as the US. In addition, the US has supposedly been supplying Russia with weapons and resources for decades now. That's not something that we would take lightly, and that's not something that Russia would want to jeopardize.
Now for North Korea: US forces need to keep a watchful eye on North Korea just to make sure that Kim Jong Un doesn't overstep his bounds, but NK just doesn't have the power to pose a legitimate threat to the security of the US.
Finally, China: China has more manpower, and possibly some military strength, but China has no reason to attack us, and no mass methods to launch a large-scale assault on US or any distant foreign target. Not to mention that they are a Communist republic, which economists have projected will face a financial crisis in approximately 5 years, and violent revolution in 10. But the real feather in the cap is that they own our debt, and are using our corporate presence to further legitimize their business industry. They have us in their pocket, and realize that we pose a far greater threat to them militarily. They don't want to attack us, because they think we are chomping at the bit to level them and declare ourselves debt free. Quite frankly, they want to hold on to that money for as long as they can.
If that doesn't ease your paranoia, then take these two factors as well. 1) The US has even more highly advanced weaponry than the public can speculate about. 2) The majority of this arsenal can be deployed and ready to fire on any target in the world within minutes.
Yes Russia can be scary, but Putin is not an idiot, were not going into a world war... Even if the UN sent in fighter jets, or troops on the ground in Ukraine, Russia would not launch a third world war, since it would instantly mean the end of the world, and everyone agrees on not doing that.
The US has always been paranoid, but this is ludicrous. They are not the red army anymore. If america is so afraid of socialism, then they would nuke Scandinavia.