Well, that's a thought. Although I think you're mistaken in the larger sense, to think that really big disturbances and instability overseas somehow works to our advantage. If anything, we depend more than ever on the Navy to protect trading sea lanes and to prevent other countries from enforcing LOST and huge seabed territorial grabs, claims of exclusivity (the Chinese have declared the South China and Yellow Seas and Formosa Strait all to be mare clausum -- we just violated their defi with a CBG transit [the Vinson or the Stennis, I forget which], tho' the Media pretended not to notice), water-column and fisheries claims, and so on.
IMO, we should be making a few territorial seabed grabs of our own. Treating them as a commons has been a disaster environmentally. Seabed mining is very expensive and there are increasing substitutes for what were once thought irreplaceable elemental resources. There are also hazards that would be very difficult to mitigate. Meanwhile, a lot of the rationale for that maritime mining effort has originated because of environmental exclusions on land that need to end.
Moreover, a lot of the problems with maritime wildlife productivity originate because we allow other countries to extract at will as a sweetener for holding our inflated bonds. Many of the agencies supposedly dedicated to protecting maritime wildlife actually have a demonstrable interest in failure. Those two combine into an ugly picture.
That said, I'm talking a larger principle here: Natural Law competition. America has been propping up socialism for nearly 100 years, especially during the Roosevelt era. The cost of doing so has abetted its metastacizing on our shores. If Europe had paid for its defense, would the left be citing it as such a model to emulate? Yet the big gains we have made against socialism were when we allowed it to fail by unshackling ourselves, particularly because the rest of the world saw it fail. Reagan deregulated the oil market and cut back on regulatory suppression and the resulting fall in oil prices collapsed Soviet cash flow. Yet if we prop up socialism, as the EU has done in Greece, look what happened to Greece. It is exactly analogous to how welfare destroyed the black family.
On the domestic side, that "Pax Americana" has operated as a subsidy by which to export American jobs and technology. The beneficiaries do not pay for that protection. Those who developed that technology in expectation of continued employment bear that exclusive and disproportionate burden of paying taxes to subsidize the export of their jobs. The extremely wealthy use tax-exempt "charitable" foundations to fund said green groups lawyers to sue a complicit agency for control of the resource by which to improve the tax-sheltered returns on their foreign investments. So you can see that said "Pax Americana" is more than just a financial burden.
I'm not talking about a complete withdrawal, but I promise you: Letting Europe for example defend itself would wake those babies up in a hurry. "Nation-building" was a success there and in Japan, but it backfires way too often as we move down the cultural ladder to the point that it is an exercise in futility in an Islamic country, central Asia (but I repeat myself), or in most of Africa. We should have stomped Iraq and gone home. Had Iran attacked them, stomp them too, quickly and cheaply, and then go home ala Barbary Pirates. They will learn how to act very quickly. I frankly think that the world would accelerate faster toward peace and civility with a better example of leadership.