Here's the thing. The United States military, historically, was almost never prepared for the wars the country wound up fighting. The Barbary Coast conflict stretched the tiny military to the limit. The Quasi-War with France was a victory only because of the significant quality advantage of US ships over French ones. 1812 may have been a strategic victory, but the significant tactical losses caused by unreadiness (US ships proved to be much more than a match for anything smaller than a line-of-battle-ship, but were far too few in number to make much difference; while the US lost most of the land battles before a force of Regulars were trained, but won the last couple) were a heavy blow to national pride and limited the strategic victory. The Mexican War was an exception. The Civil War found neither side comprehending the power of new weapons and transportation, and both sides were unable to raise troops very quicly even with conscription because of the limited training capability. The Spanish-American war was another exception, but this was due almost exclusively to the waning might of the Spanish Empire. WWI is a little questionable because of the isolationist movement delaying the war to the point where American prepardness was of limited importance (which is a tragedy, US involment earlier probably would have ended the war much quicker, but I can elaborate on that later) WWII would have found the nation all-but-unarmed (in terms of air and land forces) were it not for Lend-Lease. Korea would never even have happened if Truman hadn't made massive drawdowns because of his confidence in the nuclear monopoly.
Just because the risk of a war between Russia and mainland Europe is very ulikely now, the US is still committed by the North Atlantic Treaty to defend against such an attack now or in future. South Korea may be able to hold out against a North Korean assault, but the US is commited to defend against one. The Phillipenes have been skirmishing with China recently. (Note that these treaties are all one-way. The US is pledged to defend Europe, but Europe is not pledged to defend the US.) Thanks to a history of unreadiness, modern US doctrine is to be able to fight any two of these wars simultaneously The pace of modern warfare dictates that size-ups are not an option. You have to go to war with the army you have, if you don't have one, the other guy wins. No matter how powerful your carrier is, if it's cruising off the coast of Saudi Arabia mounting airstrikes into Lybia or Iran in support of UN operations, it's not going to keep Kim from dashing south across the DMZ. That's why the US has so many carriers. As for ground forces, despite the US's absolute numerical superiority over any likely foe, it's almost a guarantee that forces in theatre (wherever that theatre might be) are going to be facing superior numbers in the crucial opening days of a conflict. To put things bluntly, unless dozens of treaties are renegotiated, the US literally cannot reduce its forces very much.
That's not to say that cuts cannot or should not be made. Cancelling two of the versions of the F-23 would save quite a lot of money, as would cancelling the B-3. Streamlining the aquisition process is a good idea.