I personally do not find a major conflict between national armies to be likely anytime soon. Globalization has expanded the economies of the world into a fragile interdependent network and any major war would likely cause a catastrophic worldwide economic crisis that would set the entire world back decades, not only the war's participants. Just look at the drastic economic consequences circling the planet recently, caused by relatively minor events. Peace has made the world very rich. I think even recent bogeyman China is seeing just how much value they're getting out of peace and (growing) freedom. That, and their over-abundance of single-child families causes me to suspect they'd be very reluctant to commit to a war where they stand to lose a lot of troops.
Specifically in regards to the US, given its geography, it would be easy for it to depend on itself, but not without first undergoing an earth-shattering breakdown of its economy and society. Therefore I think a policy of maintaining a military just to defend itself is a faulty notion. Peace in other countries is very directly beneficial to it. I think a much bigger threat to the US(and the rest of the world) is that modern(and future) technology allows individuals and small groups to wield massive destructive power. So, while I do support a slimming down of the US conventional military, I think a growing/strengthening of specialized forces able to thwart these small groups is of great importance.
In regards to the US' foreign policy, if one can take at face-value it's claim that it is willing to pay in blood and treasure to protect the freedoms of individuals across the world without asking anything in return, well, thats a pretty damn amazing thing. The history of the world is rife with conquering superpowers who weren't quite so generous.
And while its safe to assume that the intentions of the US aren't always so altruistic, one cannot deny that there are a lot of nations and peoples of the world that owe their freedom/safety/existence to the US military. Heck, there's a even an argument to be made that the US Navy is responsible for safe oceans over the past 70s years that allowed rapidly growing and successful ocean-based shipping and trade. Fact of the matter is, if the US is making the world safer, then everyone is benefitting in very real ways, even it's detractors.
Now, I'm not saying what the US does is always good, but I think people often overlook the good in favor of the bad. Personally, I dont think that worldwide democracy, freedom, and safety for individuals is a bad goal. The problem is, not everyone agrees with that and they're willing to go to war to prevent it.
And since the thread has turned that way, I want to add that I politely object to the usage of the term "Islamophobia". Its a loaded term that carries a negative connotation that in and of itself belittles opposition and stifles rational discussion. A phobia is defined as an irrational fear so the word implies that anyone who has a beef with Islam is a loon that needs to go consult a shrink. Personally, I am generally opposed to all religions, but I find Islam to be head and shoulders above the rest as a source for legitimate complaints.