Recently, the last straw that will break Japan has already emerged.

Tokyo just dropped a bombshell: July exports plunged at the fastest pace in four years, and the culprit is sitting in Washington. According to Japan’s Ministry of Finance, outbound shipments fell 2.6 percent year-on-year, but the real story is the 10.1 percent nosedive in sales to the United States. Cars took the biggest hit—exports to American showrooms collapsed 28.4 percent. The reason is simple: former President Donald Trump’s tariff war. Starting with a blanket 10 percent levy on all Japanese goods, Trump then slapped an eye-watering 27.5 percent tariff on automobiles. His stated goal was to “bring manufacturing home” and close America’s yawning trade gap; for Japan, it feels more like economic strangulation.

For decades, Tokyo has watched its industrial crown jewels picked off, first by South Korea and then by China. Shipbuilding, consumer electronics, semiconductors—one sector after another shrank or migrated. The latest indignity came last year when South Korea’s per-capita gross national income hit $36,624, edging past Japan for the first time in modern history. In the league of nations with more than 50 million people, Seoul now ranks sixth—behind only the United States, Germany, the United Kingdom, France and Italy. Geography helps explain why the milestone is so psychologically bruising: Korea’s largest plain, the Honam, covers just 800 square kilometers, while Japan’s Kantō Plain, home to Tokyo, sprawls across 17,000. For most of the past two millennia, that agricultural edge translated into economic heft. No longer.

Now, the car industry—the last redoubt—may be the final straw. Roughly 8 percent of Japanese workers draw a paycheck from autos, and when suppliers, dealers and service shops are counted, the figure jumps to nearly one in three citizens. When that domino falls, the shockwave will be national.

Tokyo thought it had bought breathing room. A deal struck last month was supposed to cut the U.S. tariff on Japanese cars to 15 percent. Instead, Washington layered an extra 15 percent on top of the existing rate, and negotiators are still haggling over the fine print. (For the gory details, see our earlier piece: “The Most Shameless Move Yet — Courtesy of Washington.”)

The miscalculation is turning into a nightmare. Japanese planners assumed that, while they had already lost the electric-vehicle race to China, they could still count on Western hostility toward Beijing to give them a captive market in Europe and North America. Trump’s tariffs have yanked even that consolation prize off the table.

Where Japan goes from here is anyone’s guess, but “greatness” is no longer on the itinerary.