IT WAS a sky’s-the-limit moment the other day when the leaders of North America’s three major soccer federations — from the United States, Mexico and Canada — announced from the observatory floor of the continent’s tallest building that they would bid jointly to host the 2026 World Cup. As when an exchange of ping-pong players heralded a thaw between the United States and China in the early 1970s, a sporting initiative carried the symbolic weight of a diplomatic coup.

The news conference on the 102nd floor of One World Trade Center in Manhattan immediately made what The Post’s Steven Goff dubbed “the NAFTA World Cup” the odds-on favorite to win rights to stage a month-long mega-event that could generate $1 billion in revenue and attract millions of fans across 20 or more cities, most of them in the United States.

More than that, as an act of neighborliness and cooperation, it was a resounding counterpoint to Washington’s ragged regional relations, particularly with Mexico, and the Trump administration’s enthusiasm for building a border wall. Conceivably, the United States might have been the strongest contender for the Cup even if it had made a solo bid, but doing so would have required it to surmount, on its own, the negative effects of rising nativism and the White House’s dismissive and hostile remarks directed at friends and foes alike.

By standing with its neighbors, the U.S. soccer federation sent a message that the United States’ borders would be open to fans, officials and players from participating FIFA member countries — including Mexico and Iran, among others. That was reinforced by the U.S. federation chief, Sunil Gulati, who made a point of saying that Mr. Trump had encouraged the three-way bid and was “especially pleased” about the partnership with Mexico.

Mexico would host just 10 of the cup’s 80 matches, as would Canada; the other 60 would be held in a dozen or more U.S. cities. Still, many Mexican commentators, mindful of their slim chances at beating the United States in a head-to-head competition, were pleased.

Instead of mounting a problematic bid from a behemoth not currently winning any international popularity contests, the U.S. soccer federation, with its bid, now stands at the head of a juggernaut representing a combined North American population of 500 million, arm-in-arm with Mexico, host of two previous World Cups, in 1970 and 1986. (The only one hosted by the United States, in 1994, set records that still stand for average and overall attendance.)

It will likely be three years before FIFA’s 200-odd members vote on the bids. Conceivably, an African confederation could mount a strong challenge to host the event. But for now, the United States’ soccer officials have grasped what has lately eluded its political ones — what Mr. Gulati called the “hugely positive signal and symbol of what we can do together in unifying people.”