I think garrison is the wrong word for it because it denotes passivity. The idea is still to have a powerful and flexible USMC that is highly proficient in network centric warfare. It's just that the focus is increasingly on a strategic defensive posture oriented around great power competition conflict. The U.S. can afford to take the strategic defensive since China is the revisionist power while the U.S. is the status quo power. Operationally speaking, it means to avoid the need for costly break in operations against the Chinese anti-access arsenal by reinforcing the forward presence (largely along the first island chain, and increasingly northern Australia and other Pacific Island nations), and a survivable one at that (which increasingly means dispersed).
As to the actual geostrategy.... well, there is no unified geostrategic outlook besides the consensus that China is the benchmark adversary and to a degree a strategy of containment is being pursued. IMO, there is a real dearth of geostrategic thinking in the U.S right now, and it didn't help that a number of great thinkers like Andy Marshall of the ONA have passed or moved on. You touch upon this with some of your comments, but basically a huge part of this is the serious dysfunction and lack of unity between the two parties - good luck trying to come up with a serious long-term strategic plan when there is little continuity and the focus could shift when the next President assumes power. That is why I laugh when I read that the Navy's upcoming force structure review will call for 534 ships. Not that I blame the Navy, we just have to be realistic about the lack of stability right now which really impacts on long term planning and geostrategic policy implementation.
In my opinion, there has been a lack of serious geostrategic thinking, based upon Realpolitik, in the upper echelons of the U.S. government since World War II. Far too often, nefarious operatives more interested in their Wall-Street business partners and clients, such as the Dulles brothers, have carved out their own private imperial provinces (at the State Department and CIA) and directed foreign policy for the benefit of their multinational clients in place of serious thinking based upon Realpolitik and the national interest. At other times, second-rate legacy graduates from Harvard (which seems to have some special connection to Washington), such as McNamara, have led the nation's foreign policy into disasters based upon simple-minded foolishness.
No one, in my opinion, did more damage to American foreign policy, however, than Kissinger (another Harvard fellow) who promoted what he called Realpolitik, but fundamentally misunderstood what Realpolitik was for 19th-century Germany and what it implied for America's global position during the Cold War period.
When we speak of "globalization," what we are really speaking about is "westernization." This must be clear before we can approach geo-strategic issues from the perspective of Realpolitik, and this is where Kissinger went wrong. Realpolitik is the strategic use the power of the state in a pragmatic manner to promote Enlightenment thinking so far as possible within the constraints of the real world. Maintaining open sealanes, free of piracy and other dangers, for example, would be a goal of Realpolitik, and one that the U.S. has pursued successfully.
Unfortunately, instead of the values of the Enlightenment, Kissinger viewed consensus as the ultimate basis for global stability. He felt if he could build consensus between China, Russia, The U.S. and Western Europe, then even the Communist nations would somehow, by magic maybe, conform themselves to Enlightenment, liberal ideas. This is why he pursued detante with Communist Russia and naively thought that he could open Communist China to free trade. He thought that by building consensus, he was building long-term stability. He wanted to be the Metternich of his age, but his was not the age of Metternich, and no long-term consensus can be built between nations that pursue free trade and open sea lanes and Communist nations that view all forms of commerce as inherently illicit.
The lesson of the first two world wars was that colonial mercantilism and the unrestrained national competition for resources leads to global wars. The alternative was a system of exchange in an international marketplace rather than in walled-off colonial fiefdoms. While the U.S. has done an excellent job after the Second World War of securing international trade routes and incorporating former colonial rivals, such as England, Japan, and Germany, into a Pax-Americana market, they have never successfully incorporated China or Russia into that order.
With Russia, the opportunity was there to do so in 1989, but again there was little or no geo-strategic thinking. Kissinger's detente (which then would have been appropriate for Russia in terms of Realpolitik) was replaced with neo-con, Wall-Street-style imperialism, ala Dulles. Russia was looted by Wall-Street financiers and their friends in Russia (whom the media now refers to as "oligarchs")and never properly incorporated into the Pax-Americana.
As a result of Kissinger's desperation for consensus at all costs, China now has converted itself into a modern mercantile nation that has rejected the lessons of the first two world wars and seeks to gain access to ever more resources to fuel its domestic industry. Such mercantile ambitions cannot be checked by a mere policy of containment, and as more and more nations are transformed into resource colonies for China, what little stability there is globally will shatter.
You are right. The U.S. is in desperate need of some serious geo-strategic thinking based on Realpolitik. However, I am not certain that those capable of doing so will ever occupy the positions that direct the country.
Disagree with your assessment of Kissinger wanting concensus.
IIRC, Kissinger's doctoral thesis, and if it wasn't that, it was certainly the theme of his main scholarly book (which I read so many years ago I've forgotten its title) was the interplay of an uneven number of Great Powers. Which meant Europe primarily in the 1700s. It was the balancing act between them which most exercised Kissinger's mind.