The American people are dangerously divided, but one event looming on the horizon has the potential to put us on a path toward unity: the U.S. census.

If President Trump makes no changes, the U.S. Census Bureau in 2020 will again seek to shoehorn some 330 million Americans into official racial and ethnic categories. This system doesn’t just ignore science. It also completely overlooks a burgeoning “mixed-race” population that resents arbitrary racial straitjackets.

Why this unnecessary division? Because for four decades our government has been engaged in the unsavory practice of designating official groups, and standing against any reform is a coalition of special-interest liberal organizations that depend on it for funds and prestige.

Changing this status quo is therefore a fight that Trump should relish. If he doesn’t, the United States will continue its present evolution from a nation-state into a “state of nations” — something more akin to the Ottoman Empire, where people were stratified legally based on ethnicity and religion.

The president has the power to change the census. Many Americans believe that the division into five ethnicities — white, black, Hispanic, Asian and Native American — has been around for as long as we’ve been collecting census data. Not so. The system goes back only to 1977, when the Office of Management and Budget issued Statistical Policy Directive No. 15.

The groups were then jammed into the 1980 Census, with no input from voters. Science also didn’t get a vote: Bureaucrats conjured up pan-ethnic groups such as “Hispanics” and “Asians” with no basis in anthropology, biology or culture. Today, this regime stands behind the identity-consciousness that is tearing the nation apart. Obviously, we need another approach.

The Trump administration wants to change the census by asking a question on citizenship. Though important and with historical precedent, that modification doesn’t go far enough. A more valuable reform would include getting rid of the official categories and asking simple national-origin questions (“Are your ancestors from Ecuador, Germany, Japan? Check as many boxes as apply.”) and, perhaps, questions on races identified by anthropologists — not bureaucrats.

But even these are too reductionist. Today, you can spit into a vial, send it to genomics companies and discover that you are not “Irish,” as you thought, but instead 60 percent English. Or you could be roughly 30 percent German, 45 percent Slavic, 15 percent Native American and 10 percent Bantu. The census’s official categories ignore this rich diversity.

Of late, mixed-race Americans who balk at being straitjacketed have gained a high-profile defender: Meghan Markle, the American engaged to Britain’s Prince Harry. Markle detailed in Elle magazine a personal experience in her seventh-grade class that involved a mandatory census with only the standard race-box options.

When she complained, the teacher told her to check Caucasian “because that’s how you look, Meghan.” But she couldn’t do that and hurt her African American mom’s feelings. When she told her father that night, he responded sagely, “If that happens again, you draw your own box.”

Opposing this common-sense approach are the leaders of ethnic special-interest organizations such as UnidosUS, Asian Americans Advancing Justice, the National Association of Latino Elected and Appointed Officials and many others. They, along with academics from “critical theory” departments — the census “stakeholders” — have enormous influence over the racial questions in the census. Some have already come out strongly against the administration’s proposed citizenship question, saying — without any evidence — that it will suppress responses by immigrants.

Such organizations benefit from billions of dollars in taxpayer money apportioned based on census data, as well as their ability to raise money privately. They justify the division of the country by claiming that civil rights enforcement depends on the census data. In fact, during the Obama administration, it was proposed that the Census Bureau add yet another pan-ethnic group for Americans with ancestry in the Middle East and North Africa.

But the official categories often shed little light on policymaking. Groups such as “Asians” and “Hispanics” do not capture the different life experiences of Indian Americans and Korean Americans or Mexican Americans and Cuban Americans.

Trump has broad powers to say “Enough!” As president-elect, he complained to a crowd in Cincinnati, “For too long Washington has tried to put us in boxes. They separate us by race, by age, by income, by place of birth and by geography. They spend too much time focusing on what divides us.”

It’s well past time to recognize that the four-decade experiment has failed and has put our nation on the road to becoming merely a collection of tribes rather than one “indivisible,” as our creed proclaims. Reforming the outmoded census would reflect the reality of our population and accentuate our identity as Americans.