It was February 2017 and President Trump’s first address to a joint session of Congress. I was on the floor of the U.S. House as a guest of a pro-trade Republican congressman. As the president announced the U.S. withdrawal from the Trans-Pacific Partnership, I was thinking about a conversation I’d had with a particularly astute Asian ambassador. He’d suggested to me that if a book on the decline of American influence in Asia and the Indo-Pacific were ever written—and he hoped it never would be—its first chapter would be an account of the withdrawal of the U.S. from TPP.

Largely...

Illustration: David Gothard

It was February 2017 and President Trump’s first address to a joint session of Congress. I was on the floor of the U.S. House as a guest of a pro-trade Republican congressman. As the president announced the U.S. withdrawal from the Trans-Pacific Partnership, I was thinking about a conversation I’d had with a particularly astute Asian ambassador. He’d suggested to me that if a book on the decline of American influence in Asia and the Indo-Pacific were ever written—and he hoped it never would be—its first chapter would be an account of the withdrawal of the U.S. from TPP.

Largely because of Japan’s courageous decision to proceed without the U.S., TPP survived. With some changes to a few of its provisions and a new moniker—Comprehensive and Progressive TPP, or CPTPP—it went ahead. Nothing would have been possible if Japan, by far the dominant remaining economy in the agreement, had decided differently.

China’s decision this month to apply for CPTPP membership should be a sharp reminder to Republicans and Democrats alike that if the U.S. is serious about competing with China in the Indo-Pacific it must confront a central reality: Having withdrawn from the TPP, the U.S. doesn’t yet have a trade strategy to back up its military posture in the region. China is the principal trading partner of many countries in the Indo-Pacific. The size of China’s economy, as well as its military and geostrategic ambition, means that Beijing will be at the center of the debate over every regional and global issue in the 21st century, from climate change to trade. Its ability to influence the outcomes of those issues will be determined by the degree—and effectiveness—of U.S. engagement.

We don’t yet know where the new policy script that the Chinese Communist Party is now writing will lead the world’s second-largest economy. When Deng Xiaoping 40 years ago shifted China toward growth and an open economy with his slogan “to be rich is glorious,” it was the beginning of the largest poverty-reduction program in human history. Hundreds of millions of Chinese were lifted out of destitution, and huge opportunities opened up for China’s trading partners. Things have been moving backward lately, in the direction of greater centralization and state control. One could even mount an elegant argument that China itself needs balance from the full engagement of the U.S. in the region.

The Chinese people have benefited enormously, not from “wolf warrior” diplomacy, but from Beijing’s positive engagement with the U.S.-designed liberal economic architecture. China’s future choices and trade strategies will be fundamentally different if they aren’t constrained by a muscular and successful U.S. economic strategy in the Indo-Pacific.

Intriguingly, the U.S. is putting in place the elements of regional re-engagement. No foreign policy (or trade policy) is politically sustainable without a solid domestic constituency behind it. Trade has long been a tortured issue in American politics, particularly for Democrats, because economic change creates anxiety for the middle class. When people are under severe economic pressure, trade is always a potential scapegoat.

In September 2020, the Carnegie Foundation for International Peace published a white paper titled “Making U.S. Foreign Policy Work Better for the Middle Class.” Among the authors was Jake Sullivan, now President Biden’s national security adviser. The White House approach to assuaging traditional Democratic fears of trade-induced economic change seems clear: Shore up domestic policy before moving forward aggressively on any trade deals.

The recent establishment of the Aukus security arrangement among the U.S., the U.K. and Australia can leave no doubt that the Biden administration views the Indo-Pacific as the most important theater of strategic competition with China. Kurt Campbell, the National Security Council’s coordinator for the Indo-Pacific, has made clear that U.S. strategy in the region must extend beyond a military plan to protect American allies from China’s expansionist ambitions. It needs an economic component.

In my view, the U.S. is unlikely to rectify the mistake of leaving TPP by asking to join CPTPP. Mr. Biden has said he would oppose joining the original deal without a renegotiation. That alone would make it difficult for the U.S. to waltz back in. But it’s also true that the strategic environment has evolved. Large parts of TPP, such as its provisions on trade and the environment, remain relevant, but the past five years have sharpened the policy world’s understanding of such key issues as digital trade and state-owned enterprises. Plus, there is a new kid on the TPP block: the U.K. The world’s sixth-largest economy, a major intelligence and defense partner of the U.S., wants to join the club. The U.K.’s post-Brexit desire to expand its horizons beyond geographical Europe was the political subtext of the trade deal announced this summer between London and Canberra.

Whatever next year’s congressional elections bring, active foreign-policy engagement always requires the involvement of both American political parties. The U.S.-Mexico-Canada agreement, updating the North American Free Trade Agreement, passed easily with bipartisan support during the Trump administration. If the U.S. recommits to TPP, it should be rechristened the Indo-Pacific Economic Partnership Agreement. A new name might make it an easier sell politically.

The regional stakes were high even before China’s aggressive move on Hong Kong, its saber-rattling in Taiwan, and its ramped-up trade war with Australia. We now need to hear American leaders on both sides of the aisle talking about re-engaging in the region, not only on the political and military levels, but on the trade and economic architecture that will shape economic relations over the next decade and beyond. Only then will my friend the astute Asian ambassador be able to rest easy, secure in the knowledge that the decline of American influence in the Indo-Pacific is a book that will never be written.

Mr. Groser served as New Zealand’s trade minister (2008–15) and ambassador to the U.S. (2016–18).

Main Street: If Joe Biden intends to outcompete Beijing, surely Milton Friedman still offers a more compelling model than simply copying the government-directed approach of Xi Jinping. Images: AP/Getty Images Composite: Mark Kelly The Wall Street Journal Interactive Edition