I think (and hope) people are starting to realize that proxy wars are becoming increasingly commonplace in a world of nuclear mutually assured destruction. World actors can no longer fight each other head to head and thus fight via proxies for some relatively insignificant purpose. In a post-Cold War, post-Iraq mess, people are less willing to throw dead bodies at a shadow war fighting for a who's dick is bigger chunk of world favoritism. A desire for a return to isolationism will increase until there is a war fighting purpose that legitimately resounds with the general population. That's not to say wars won't continue as the defense contractors gotta get paid so that they can re-elect politicians.... But the populace's support for them won't be significant.

We saw a lot of ire with operations in Syria, Libya, tough talk with Iran, and now Ukraine. The Russians will be able to get away with what they want because the West's population doesn't want to get involved in something insignificant just to put the Russians in their place. So, as a representative of public support, President Obama is completely limited on what he can do to Russia. You may be of the opinion that he should talk tough, kill millions of Americans in war to prove a point, nuke everybody to save the Ukraine from Red Russia but most people will be as quick to tell you to sit down and shut up as they were with taking military action in Syria.