See 
here. A taste:
West’s failure to distinguish political philosophy from political 
theory makes it too easy for him to dismiss competing interpretations of
 the Founders’ work and its vulnerabilities. We who teach in the field 
often elide the terms when we describe what we do to our colleagues in 
political science, on the one hand, and to those in the departments of 
philosophy on the other. But in speaking of the political theory of the 
Founding, West dodges the question of its relation to the account of 
natural rights and natural law in political philosophers such as Thomas 
Hobbes and John Locke.
He uses Locke from time to time to clarify and elaborate the 
Founders’ theory, as I say, but he backs away from him whenever the 
Founders did not agree with his conclusions. This prompts one to wonder,
 did the Founders pull back from logical implications they did not want 
to face, or did they find Locke’s theory philosophically inadequate?
West can only refute the amalgam theory—the view that the Founders 
drew on philosophically distinct and therefore philosophically 
incompatible political philosophies or fundamental traditions—if he can 
show that the Founders dismissed Locke for theoretical reasons, not just
 to avoid facing the practical consequences his principles demanded (for
 example, permitting divorce). The argument of Leo Strauss in the first 
place, and his successors such as Harvey Mansfield and Thomas Pangle, is
 that there are aspects of Locke’s political philosophy, not least its 
deep indebtedness to Hobbes’ philosophy, that lead eventually but 
inexorably to the materialist individualism and anomie of our current 
predicament—in other words, toward a crisis of liberalism—and that 
insofar as the Founders invited Locke into their homes and made his 
theoretical framework their own, they risked undermining their 
handiwork.
In short, if the Founding is Lockean, it is no amalgam, but it is 
unstable, carrying with it untoward Lockean consequences. If it is only 
partially Lockean, it might avoid the bad consequences, but would do so 
by being less pure (by being amalgamated). To be less abstract: The 
weakening of the family, enormous economic inequality, and maybe even 
eventual recourse to executive predominance arguably follow from Lockean
 political philosophy even if none of this is what the Founders had in 
mind.
See also 
this comment which links to how West has responded to a similar criticism. A taste, quoting West:
“In regard to the decline of our current world… our world is the way it 
is not because of the Founding, but something else that happened in the 
last two hundred and some years… if you look at the history of western 
countries in the 1960s, all of them went through the exact same 
metamorphosis, almost at the same moment. And so, countries for example 
like Germany and Britain, that have long had establishment of religion, 
official churches and all the things that the Americans didn’t do all 
had that exact same thing. There was immediate institution of no-fault 
divorce throughout the world in the 1970s in almost every country, 
immediate institution of barriers on employers in terms of their freedom
 of contract with their employees. There was a complete collapse of 
sexual mores throughout the Western world all at once, whether it was 
New Zealand, Australia, Germany, England America.
This is not due to the Founding Fathers, I can assure you of that… 
Nietzsche’s diagnosis of what’s wrong with us- that’s where you need to 
go to understand our current situation. It’s a psychological malady that
 is a profound indication of a deep dissatisfaction in the Western soul 
now that it has gotten rid of God, now that it has gotten rid of nature,
 and reason- it has gotten rid of all meaning in human life. It has put 
us exactly in the situation.. Tocqueville worried about, where we’re 
living in the present moment. That’s where we are, and that is not 
something that the Founding Fathers can be blamed for, and I also agree 
to some degree that is something the Founding Fathers can’t help us 
solve, that’s something we’re going to have to solve ourselves.”
I think it's absolutely true that this was an international phenomenon that affected Western culture in general, not just America in particular. Certain folks might operate with blinders and assume since America isn't Europe, let's look for particular American villains to blame -- Alfred Kinsey, Madalyn Murray O'Hair, Abbie Hoffman, etc. -- and ignore Europe. The Straussians by the way don't do this and for good reason. They understand the ideas came from continental Europe and migrated their way to America.
I like their analysis much more than that of those who fulminate against "cultural Marxism." But at least they too understand that the "Frankfurt school" whom they blame for cultural Marxism are Europeans whose thought (as well as some of their people) came to America.
I don't think however, what's quoted above from West adequately answers the claim he tries to refute. Here's why: America was founded as a liberal democracy, arguably the first modern one. Lockean ideas began in Great Britain; but GB still was no modern liberal democracy if for no other reason than they still had a throne (monarchy) and altar (state established church), things liberal democracy were meant to if not abolish, defang.
By the 1960s all of the nations in Western Europe were, like America and France, liberal democracies. Indeed, America and France influenced them in becoming such. So yes, these nations are Lockean, because they followed America and France. Yes, many of those nations, like Great Britain still had both monarchies and state established churches as they do to this day. But they are "defanged"; they are titular. As liberal democracies, they have to be.
But before these nations became liberal democracies, those institutions were not titular. There is only one area where Western state established churches and monarchies still have power, and that's that they have money. And money is power.