From 1945 to 1991, the Cold War, in which the West and the USSR competed around the globe for influence, dominated the world. However, when the USSR collapsed, the US was the world's lone superpower. Given a chance to shape the world in its own image, what transpired was a world in which the US could engage in "humanitarian" warfare, expand NATO without any interference from Moscow, and impose its will on the rest of the world.
The Pax Americana found its chief expression in the doctrine of the Neocons, who envisioned an American Century, in which this country would engage in perpetual warfare against enemies of either this country, Israel, or other American allies. Raw power was used to enforce the will of whoever was in charge of the White House. Due to technology and overwhelming force, there was no need for a draft like Vietnam. War became a spectator sport.
There were cracks in the Pax Americana prior to Crimea. Iraq and Afghanistan showed that despite the raw power of the US military, the US could only impose its will on those countries with great difficulty, at a cost of trillions of taxpayer dollars. Guerrilla warfare was still an effective counter against the use of raw power as utilized by the Pentagon. The Pax Americana encouraged terrorism as groups like Al-Qaeda, whose xenophobic interests were not taken into account in Saudi Arabia, found other ways to strike back and lure the US into war on their terms -- a long war of attrition fought in the mountains of Afghanistan.
Now, in 2014, the end of the Pax Americana has come at the hands of Vladimir Putin. The reason that American power was ineffective was because the battleground was fought on Putin's terrain. We do not buy the notion that Putin is somehow like Hitler. Putin's MO is totally different -- the battle is won before the troops are sent in. When the troops are sent in, that means that Russia has already won the conflict. We saw this in action in Georgia as well; that conflict can be regarded as a test run for Ukraine.
Being a KGB man all his life, Putin's battles are different than the raw power of the American mindset. His battles are fought in the court of public opinion, subversion, hacking, espionage, and protest. His pressure can be economic, such as jacking up the prices that Ukraine has to pay for its gas. He knows that the Americans can do little -- they are not bound by NATO to come to Ukraine's aid and a display of raw power would result in a nuclear holocaust. We'd all burn.
Since the battlefields of the 21st century are no longer decided by raw power, a completely new world is emerging, which is multipolar. The world stage is no longer the exclusive property of the nation state; anyone with a platform and a microphone can participate. Multinational corporations, Internet communities, governments, interest groups like the Right Sector or a Russian nationalist group, or even a charismatic individual can influence the course of history. Putin understands this; Russia Today, his mouthpiece to the world, is the most successful YouTube channel in history, with over 1 billion viewers.
Battles are now won in the court of public opinion and reputation just as much as they are on the military battlefield. One of the reasons America lost so much power and influence over the last decade is due to reputation -- even though George W. Bush was never impeached and removed from office for his war of aggression against Iraq, the reputation of the US as a beacon of freedom took a serious hit that it has not yet recovered from. Another blow to US reputation happened after 1990 -- when they told Russia that they would not expand NATO beyond a certain point. When a pro-US government emerged from the Euromaidan protests, it was a red line for Putin since, in his mind, the US had gone back on its word to Russia one too many times. Reputation is measured by how well one keeps their word -- exactly like it is done in Civilization, a popular computer game.
And like Civilization, a hit to one's reputation can be hard to overcome. Back during the height of the Cold War, one of the chief US tactics was regime change through the use of CIA subversion. This tactic was also used unsuccessfully in Venezuela last decade when Chavez was swept into power two days after he was driven out. Putin, of course, is well aware of the American reputation for overthrowing foreign governments that it doesn't like. This explains his increasingly draconian laws banning protest in Russia, along with his ever-stricter press controls.
To be fair, Putin does not properly understand the importance of reputation either. When he occupied Crimea, it was in violation of a 1994 treaty between the US, UK, Russia, and Ukraine in which the latter gave up its nukes in return for the other powers respecting its sovereignty. When Russia blatantly violated that treaty, Putin took such a hit to his reputation that the European powers now want as little to do with him as possible, as evidenced by Russia only getting a handful of votes of support at the UN General Assembly, getting none in the Security Council, and NATO ending all cooperation with Russia.
And since anyone with a platform and a microphone can influence public opinion and history, this gives rise to separatist movements around the world. Ukraine is hardly alone in trying to deal with separatists. Scotland is seeking to break away from Britain. Russia fought two wars against Chechen separatists in its recent past and the breakaway of Crimea could set a precedent for some other separatist movement in Russia some time down the road. And even the US has separatist movements, with established groups in Texas (Texas Nationalist Party) and Alaska (Alaska Independence Party) advocating for independence.
And finally, because this is now a multipolar world, the need for collective security has increased. Ukraine is scrambling to create collective security arrangements with neighboring countries and trying to form an association agreement with NATO, something that was off the table even with pro-western leaders in power. Russia, which has constantly sought some sort of security buffer, is seeking to form some sort of Eurasian alliance. And NATO, which was seen to be increasingly irrelevant after Iraq and Afghanistan, is suddenly relevant again. And since occupations and perpetual warfare are not such a good idea to stop terrorism and since drone warfare kills too many innocent civilians, collective security will be seen as an increasingly important tool against terrorism.