The nature of sudden collapse is that it is always preceded by gradual decay that few notice because they have nothing against which to compare the present conditions of life. This is why the young are particularly susceptible to status quo bias. As someone from an older generation, who's witnessed the sweep of events during a pivotal period, I believe decline can be limned. But circumspection is required.
Collapse doesn't happen, and doesn't happen, and doesn't happen... until it does. This is how it often goes. Vesuvius was quiescent long enough for Pompeii to have have been built in its shadow, the illusion of its benignity.
The forces behind our malaise are certainly vested in their own survival and enrichment. Some see decay as the advance of the new. For those who worship novelty, this looks like "progress." The fragility of the extant anti-culture is often overestimated by sanguine counter-revolutionaries. Scale and inertia matter.
Yet one thing is certain: God will not be mocked. We can see our cities succumbing one by one, where the conditions for the preservation of advanced technological civilization are not met. This phenomenon will spread and accelerate, as foreign replacements of the Settler and Builder Nation-who didn't create the civilization they now presume to dominate and rule- prove incapable, and, finally, undesirous of sustaining it. This effect exemplifies the magical thinking of migrants, whose common perspective can be contrasted with that of Settlers and Builders. He who acquires is not necessarily the equal of he who builds.
The presumption of racial equality spins illusions that ensnare the narcissistic and the foolhardy. Those illusions have very real repercussions in the long term, where the ability to not merely maintain, as in dead ritual, the achievements of a foreign civilization, but to also advance them, is taken for granted. I'm reminded of the imperial atomic priesthood in Issac Asimov's Foundation Trilogy. Through exacting ritual they were able to maintain the giant reactors on which civilization depended, while they had long since forgotten the principles that enabled men to build them. The ability to engage in abstract thinking is much the same. It is not equally distributed among nations, but it is absolutely essential to the formation, maintenance, and advancement of technological societies.
Mexico city is not like New Delhi because of the unavailability of concrete or electricity. It resembles that distant human slag heap because Mexicans have a national soul that is closer to the Dravidian than the Anglo-Saxon. The slow motion process of decay I'm describing, punctuated by sudden shifts of balance, terminates with the greening and shrinkage of major urban areas, accompanied by the inability of the political and economic centers of the Situs State to hold, to continue to maintain the superficial illusion of wealth and control. First moral authority is lost. Then, finally, mere power itself is lost, which cannot be exercised, ultimately, absent authority. Civilizations rot from the inside out. Foreign invasion (demographic or otherwise) is little more than a coup de grace. The old monarch drops the scepter before the rude barbarian sweeps it up.
A collapse that requires 200 years to reach terminal inertia is still a collapse, from the perspective of the sweep of history. But human life is short and such processes consume generations. They rely on the incremental nature of deep change to remain undetected until the damage is irremediable. Our great-grandchildren will be within sight of the end of the U.S. as we've come to know it.