While everyone has been worrying about a trade war between the US and China, something far more dramatic has happened between the two countries.

President Donald Trump last week signed legislation to allow high-level talks between the US and Taiwan.

That crosses a "red line" for China, violating the "One China" policy the US has had with China since the Nixon administration.

Earlier this month, a scathing editorial in Chinese state media warned the US Senate not to pass the Taiwan Travel Act, legislation to permit high-level talks between US and Taiwanese officials.

Unless US President Donald Trump "is ready to see the by and large stable and so-far profitable relationship derailed, unless he is determined to plunge his country into a pointless, mutually damaging altercation, or worse, he should resist the seducement," the editorial said.

It added: "Unlike trade, though, Taiwan is a matter of sovereignty. For Beijing, it is a clearly defined core interest that is not negotiable."

Anyway, on Friday, Trump signed the bipartisan bill into law.

On Tuesday, Chinese President Xi Jinping gave a rousing speech before the National People's Congress — the annual meeting of China's Communist Party — and he had some choice words for Taiwan (and most likely the US as well).

"All acts and tricks to split the motherland are doomed to failure and will be condemned by the people and punished by history," he said.

About a day later, China's aircraft carrier the Liaoning went into the Taiwan Strait, where it was tailed by Taiwan's military.

Non-negotiable

And so here we are, with the market gearing up to watch us haggle over soybeans and Boeing aircraft (the US's biggest exports to China, according to the Institute of International Finance) like a farmer at the Iowa State Fair — when in reality the danger is much graver.

China has for some time been warning the Trump administration against getting closer to Taiwan. In January 2017, the Chinese foreign ministry official Lu Kang did a rare, candid interview with NBC in which he said this:

"Because this issue touches upon China's core interest, by no means is this something that could be negotiated or used as a bargaining chip ... 'One China' policy, 100%."

Then, in August, still worried that the Trump administration would do the unthinkable and pass this bill, China's ambassador to the US, Cui Tiankai, sent a letter to the leaders of the congressional foreign-relations committees.

Cui said the Taiwan-related measures would be "provocations against China's sovereignty, national unity, and security interests" and "crossed the 'red line' on the stability of the China-US relationship," according to The Washington Post.

What Beijing saw in Trump was a fully transactional president at the helm of the United States — someone who thinks everything is for sale and negotiable.

When it comes to trade, that's fine. Negotiation is part of the very nature of trade, and both parties have said they will come to the table. This is a question of negotiation skill, which in this administration has yet to be tested and produce significantly positive results.

National sovereignty is another matter entirely for the Chinese. From the beginning, they've wanted Trump to understand that Taiwan is not a skyscraper or an Atlantic City casino or a nondisclosure agreement drawn up for a porn star. Instead, it is something to be taken very seriously, with long-term implications in mind.

For better or worse, the gravity of this situation did not stop the president from signing this bill into law.

Do the math

Winnie the Pooh is often used as a symbol to mock Xi. Reuters

Now, we may just be at a moment in US-China relations where our support for Taiwan must be reinforced at all costs. Perhaps that's the right move right now.

What is certain is that the calculus behind the US's support for the "One China" policy has changed.

In the 1970s, when we adopted the policy, the US wanted the Chinese to stop interfering in Vietnam, while China — far weaker then than it is now — wanted help with the USSR, with which it had fought in the Sino-Soviet border conflict in the 1960s. So you see how the policy worked for both parties.

Now, China is getting stronger and more assertive in its region, and over the past few years, it has done everything it can to push Taiwan off the global stage without actually firing a shot. For China, that means boxing the country out diplomatically — doing sweet deals with Taiwan's trading partners and pressuring countries not to help it militarily.

From the Asia defense analyst Phillip Orchard over at Geopolitical Futures (emphasis ours):

"Reunification is Beijing's utmost strategic and political priority. This view is, in part, motivated by domestic concerns. Under Xi, China is putting the finishing touches on its reintegration of Hong Kong and Macau, the two other physical reminders of China's century of humiliation and foreign subjugation.

"Taiwan is a perpetual scar on the Communist Party's narratives about the communist victory in the Chinese civil war, and the party routinely nurtures grievances about foreign meddling in Taipei to curry nationalist support for its right to rule.

"This view is also strategic. So long as the US can pair its superior naval and aerial capabilities with bases and allied support along what's known as the first island chain — Japan, Taiwan, the Philippines and Indonesia — it poses a threat to block sea lanes that are critical to China's export-dependent economy. And more than any other island in this chain, Taiwan could be used by a foreign power to threaten the Chinese mainland itself. Retaking Taiwan would blow a massive hole in the US containment strategy — and put China in a more enviable position to threaten Japan.

"For Beijing, therefore, reunification is a matter of when, not if."

Oh.