How does Louise Bryant's assessment of how the Soviet Union would fall hold up at the beginning of the 21st century?

In one thing she was right: socialism (and communism) still stays with us and shows no sign of declining or falling:-) I mean China first of all. The largest economy in the world, not speaking of he huge population.

So any explanation why Soviet Union collapsed must be based on some features which are not applicable to China. And this makes the task much more complicated.

EDIT. Of course there are differences between Soviet Union and China, but there are also big differences between Soviet Union in the 1920s and Soviet Union in 1980s.

Both Chinese and Soviet systems evolved. But I cannot understand why people deny that China remains a communist country: it is a one party dictatorship, and the ideology of this party is Communist. Considering atrocities that the government committed to their own people, China is comparable to Soviet Union. They don't do this anymore (on such scale) but the Soviets also did not in the ater time of their existence.

The Soviet Union was split apart by "centrifugal" forces because "socialism," the glue mentioned in the Bryant thesis that held it together, was too weak. Perhaps more to the point, the revolutionary fervor and "class consciousness" reported by Bryant in the early days of the Revolution that motivated it had mostly disappeared by Gorbachev's time. Put another way, the problem was not that socialism in Russia was "premature" in Russia as Bryant claimed. Instead, its power was "real" (as she observed) but had outlived its usefulness by the early 1990s.

Basically, the Soviet Union was an artificial construct of one large country and 15 smaller ones, whose main commonality was their control by the largest one. This construct depended on continued Soviet expansion, which the Reagan Doctrine halted. When Gorbachev tried to institute a more open, democratic society as the basis of reform, he fatally loosened the bonds of force that had held the "Union" together before the economic reforms had a chance to do their work.

USSR/Russian Empire fell because its government could no long contain the centrifugal forces that are present in any heterogeneous empire.

The colonies (called in the USSR for propaganda reasons "republics" who even had a nominal right to secede) always wanted out (the more recent additions were more eager to separate, the more ancient less), and were held together by (the perception of) the iron fist of the Party/Czar.

As soon as it became clear that the Center was unable to maintain it expansionism, the colonies rebelled and split off. This happened in 1917 and then again in 1989 (satellites) - 1991 (republics).

Thus the "external pressure" decried by Kenan (mention by @Semaphore) was absolutely necessary to prevent USSR's "extended empire" of republics, satellites, "countries of socialist orientation" &c, from expanding, and as long as it was expanding in at least some sense, it was stable inside.

So, the bottom line: USSR collapsed by internal pressure, which became insurmountable because the outside world stood firm in the face of the Soviet expansionism.

"The most significant fact is that it will not fall from inside pressure. Only outside, foreign, hostile intervention can destroy it."

In fact, some historians have argued the exact opposite: the Soviet Union only lasted as long as it did because the Kremlin held up a foreign enemy to distract from internal pressures. Without a boogeyman to act as a unifying force papering over domestic cracks, the Soviet Union would have imploded long before 1991. As Dr. Wade Huntley puts it:

According to this view, had it not been for a tendency toward wild-eyed anti-communism on the American side, the Soviet Union may have collapsed under its own weight much sooner than it did. The stridence and belligerency emanating from Washington, from the 1950 adoption of "NSC-68" onward, had little effect but to strengthen comparable hard-line views in the Kremlin.

_{Armstrong, David, and Erik Goldstein, eds. The End of the Cold War. Routledge, 2013.}

This theory is not the most popular with the public, but it enjoys respectable support among experts. None other than Truman's ambassador to the USSR George Kennan, who was once a leading advocate of containment, argued after the fall that:

What did the greatest damage was not our military preparations themselves, some of which (not all) were prudent and justifiable. It was rather the unnecessarily belligerent and threatening tone in which many of them were publicly carried forward. For this, both Democrats and Republicans have a share of the blame.

_{Kennan, George F. "The GOP Won the Cold War? Ridiculous." New York Times 28 (1992): A15.}

In the same article, Kenan further advanced another theory, namely that the actions or policies of the West - chiefly the United States - were actually not very important. He implicitly affirms the idea that the Soviet Union fell to domestic factors, dismissing the idea that an external power could cause such domestic upheaval as "childish". In this view, the Western allies were little more than bystanders, witnessing the fall of the Soviet Union to internal pressures.

Louise Bryant's predictions, while certainly idealistic, were also an understandable product of her circumstances.

Vladimir Lenin, the founder of the Soviet state, once said that the struggle between socialism and capitalism would ultimately be decided by the productivity each side was able to achieve, not on the battlefield. And he was right in essence, if not wrong in picking the winning side.

_{Pechatnov, Vladimir. "Soviet-American Relations Through the Cold War." The Oxford Handbook of the Cold War. Immerman, Richard H., and Petra Goedde, eds. Oxford University Press, 2013.}

When Byrant wrote her Six Red Months in Russia in 1918, it was not unreasonable to make the same mistake as Lenin. Communism was still essentially theoretical; the idealistic belief that it could compete favourably against capitalism in terms of economic output had not yet been undermined by decades of underwhelming reality.

Meanwhile, belief in the inevitability of class war underpinned the ideology. In fact, shortly before her book was published, the Allies did intervene against the Communist revolutionaries. Had their attempt to prop up the White Army worked, Byrant would've been completely correct.

What this really shows, is that predictions of the future rarely works out.

Of course, as you pointed out, there's still considerable debate over the exact causes of the Soviet collapse. Which make sense- the Roman Empire fell in the West over 1500 years ago and entire careers are still being made debating why it happened.

However, it's important to note that even those who attribute credit to American administrations, generally do not dispute the fact that the Soviet collapsed under domestic tension. No one contends that a foreign invasion ended the Communist government, as Louise Bryant thought would happen.

Instead, the primarily debate is whether the Soviet collapse was inevitable, and to what extent the Western Allies added to that pressure.

In the end, George Kennan's view that the Soviet Union would collapse under its own weight was accurate. Whether U.S. actions increased that weight or whether collapse was inevitable on its own schedule remains unknown.

_{Watson, Cynthia Ann. U.S. National Security: A Reference Handbook. Abc-clio, 2002.}