WI if there was no proliferation of policy "think tanks" in the U.S. in the 1960s and 1970s? Corporations, academia and government institutions have their research arms, but there is no subsidized infrastructure for policy research. This could have profound impacts across many policy areas but possibly the most profound on US foreign policy.
To a great degree, "think-tanks" like Brookings and the Center for Strategic and International studies function as a holding pen for out-of-office experts ready to be political appontees when their own party or faction of a party returns to power. Left, right and center think-tanks all exist, but they are heavily weighted to the right.
Possibly without think-tanks domestic conservative reforms in the 1980s and 1990s may occur, but in a somewhat different form, as part of more straightforward and undisguised bargains between politicians, business, pressure group, labor and consumer interests.
On foreign policy the main divergences are likely to come at the end of the Cold War.
In OTL, foreign policy oriented think-tanks in the U.S., probably with the sole exception of the CATO institute, busily threw themselves into the task of rationalizing a continuation and expansion of the U.S. global military role and alliances.
There had been talk in the late 1980s about US global over-extension in terms of its military commitments, and much talk about how Japan in particular, but also Germany, were gaining an industrial competitive advantage, in part by free-riding on U.S. security commitments. Libertarians and writers decrying declining U.S. competitiveness looked forward to a "peace dividend" and advocated pulling the U.S. out of its security commitment to Japan, especially as the east bloc dismantled itself.
However, this process never got very far. Permanent deployed military forces in Europe and Japan, and the overall U.S. military, did shrink from their Reagan era peak, but the only base the U.S. left was Clark and Subic in the Philippines, when the U.S. decided to decline to pay the extortionary rental rates Manila asked for. There was no sunset on other commitments, and from Desert Shield onward the U.S. became more deeply committed to the Persian Gulf.
Think tanks played an important role setting the parameters of acceptable debate. Those with a foreign policy focus, mostly of the center and right, uniformly appointed themselves a guardians against the "specter of isolationism" and fretted that withdrawing from any Cold War commitments, or even just refusing to embark on new military commitments, equated with 1930s style isolationism.
Their interest in doing so was obvious. After the end of the Cold War, how else could former Sovietologists, or Soviet-bloc-ologists and experts in European security affairs at think-tanks keep themselves relevant and employable except by arguing that there was a compelling U.S. interest to fill security vacuums in Central Europe?
If there were no more security interests after the Cold War, and you were an expert on the military and politics instead of trade or finance, you were obsolete.
So, think tanks did a full court press to rationalize new domino theories of instability and to find vital U.S. security interests in the Yugoslavian break-up and the Central European vacuum. The U.S. acquired a rationale to continue paying for its forward forces in Germany instead of shifting spending elsewhere or cutting taxes. Think-tankers had a vested interest in keeping alive foreign policy by historical analogy, with isolationism as the greatest curse, and every region of the world dready to decline into 1930s style chaos without firm U.S. security commitments.
In Asia, the similar need for security experts to stay employed led to a reemphasis on the importance of the North Korean threat, and a tacit recommitment to Taiwan's security. China, a practical ally in the late Cold War, came a state that the U.S. had to balance regionally.
The end result in policy was a much more limited post-Cold War drawdown compared to the post WWI, post WWII and post Vietnam drawdowns. Cheney and Powell kept the breaks on force and commitment reductions during the first Bush administration, and by its tail end, Paul Wolfowitz issued a document saying that the point of U.S. strategy was to prevent the reemergence of previous Cold War rivals Russia and China, and also to keep European and Pacific Rim allies "reassured" under US alliances so they would not even think about an indepdent security policy.
While the baldness of the Wolfowitz document was shocking and the government officially backpedaled from it, it remained US strategy through the Clinton years.
A big a effect of this strategy, egged on by think-tanks, was the expansion of NATO, to fill the vacuum between Germany and Russia. With the exception of CATO, think tanks almost uniformly lined up to give pro-expansion arguments more "expert" testimony and to denounce isolationism.
Think-tanks also supported the free trade consensus. To be sure business interests helped the free trade argument, but "expert" support was a tool that pro free trade business could use in arguments with other business interests that might have preferred protection.
Internationally, the think-tank culture may have played a part in getting European, Gulf and Pacific Rim elites to stay more receptive to free trade arguments and US alliances.
So, what if no think tanks?
Primary effects - no NATO expansion, a real chance at U.S. military retrenchment from Japan, korea and Europe all could have resulted from a debate where cutting back could have looked like a real budgetary savings.
The Persian Gulf is more iffy because there was a stronger perceived US economic interest in being militarily engaged there (and Saudi reimbursed the US for its 1990-1991 war costs).
The US might have had a military policy attuned to the western hemisphere and an expeditionary capable navy, still a much smaller force structure than OTL.
US allies might have found that they needed to build up their own forces and possibly build nuclear weapons, though this is not certain. The lack of immediate, blatant aggressors big enough to threaten them directly might have allowed them to still do significant post Cold War downsizing even without US forces and alliance commitments around.
The US could have had an easier time reducing its budget deficit in the 1990s, it would have not spent money intervening in the Balkans or Somalia. The second Gulf War would have been less likely because the US would have shifted to role where the burden of proof was placed more heavily on intervening instead of not intervening. However, if the US did have a second middle east war it would not have troops from Poland or South Korea helping out.
The US and Mexico might be somewhat more competitive vis-a-vis east asia, if the East Asian states felt a need to maintain larger security establishments against each other and this limited some non-military investment opportunities for them. Possible reduced competition might have been a good thing for Latin American light manufacturing, and less military spending could have caused the US to have more public and/or private investment.
I'm making the argument that experts biased in one direction, by their own interests and values, made a decisive impact on US policy debates that a straight budgetary or cost-benefit analysis might have made go another way. Thoughts?