The 73rd United Nations General Assembly opens on Tuesday in New York with world leaders bracing for the next global crisis – and the rest of us uncertain about what they would do if it comes.

Don't be fooled by the fact that U.S. markets hit record highs this past week, that global growth remains steady, or that the Trump administration in its first two years has escaped any crisis of the sort that came with the 9-11 terrorist attacks of 2001, the 2003 Iraq War or the Lehman Brothers meltdown of 2008.

In my many years of taking the global pulse around UN week, where more than 120 leaders will gather, I've seldom seen or sensed such uneasiness and uncertainty. I've never known a time when the potential sources of volatility have been so widespread geographically.

The debate, hence, has become less about the likelihood of a crisis and more about what form it might take, with what severity it will strike, and whether world leaders will have the capacity to contain it. They worry above all that America looks unbalanced to them, and thus the default source of stability during such a crisis feels like more of a wild card.

Reporters next week will focus their attention on what President Donald Trump says in his speech to the General Assembly at the opening and again a day later, when he personally chairs a special session of the UN Security Council on stopping nuclear proliferation. (Expect a mixture of vilifying Iran and praising North Korean leader Kim Jong Un, whom he branded as "rocket man" on the same stage last year.)

However, excessive focus on Trump's words would miss the more consequential story. A crisis is brewing in the cauldron of excessive debt, growing trade tensions and mounting geopolitical risk. The stakes are historic in nature during our new era of global competition, characterized by Chinese efforts to displace U.S. leadership, Russia's actions to disrupt it, and American uncertainty over how and whether to preserve it.

The list of potential sources of instability are many.

It could come in the form of economic war or financial crisis. Those odds grew this week with Trump's new tariffs on $200 billion of Chinese goods, China's return volley on $60 billion of U.S. imports and Trump's threat to turn the screw yet another notch.

It could come as a security crisis out of the Mideast, a prospect underscored by this week's Syrian shoot-down of a Russian military reconnaissance plane. Initially, Moscow blamed it on Israel, but the incident only underscores the perils of so many potent parties operating over contested territory. Mideast crises rarely remain within the region's borders, having expressed themselves as extremist ideology, terrorist strikes and refugee flows.

It could grow out of the political populism and nationalism that is unsettling Europe through Brexit, Italy's disruptive government, the rise of the German right and the new sanctioning of Hungary. European Union institutions have seldom faced so many simultaneous, centrifugal challenges

Historic shifts often come in clusters. Don't forget that the 2008-09 financial crisis, which weakened and distracted the United States, was accompanied by the Russian invasion of Georgian territory and Beijing's staging of the 2008 Summer Olympics, signaling the more assertive period ahead.

Worth watching most closely is how relations unfold with China. A U.S.-Chinese crisis, if not contained, could poison the most significant bilateral relationship for the global future.

Markets appear to be betting that Trump's new tariffs are merely another negotiating tactic, one that will ultimately result in a de-escalating deal. The real optimists even believe this trade conflict could create more value as China opens up markets and stands down from its unfair trade practices.