In his State of the Union address Tuesday, President Trump once again presented his case for a wall on the United States’ southern border. There is plenty to debate about what such a wall would accomplish, but the president has no doubt: It would keep out bad stuff, such as drugs and guns, and bad people, who commit crimes and damage the U.S. economy. 

The president’s claims about crime are factually dubious. As Christopher Ingraham noted in The Post last June, “The social-science research on immigration and crime is clear: Undocumented immigrants are considerably less likely to commit crime than native-born citizens.” Study after study rebuts the migrants-as-criminals argument. But it is the president’s characterization of migrants’ dire economic effect, and his depiction of American scarcity, with workers fighting over scraps, that also warrants debunking.

As Trump noted elsewhere in his speech — contradicting the dire economic terms of his immigration discussion — the United States is experiencing an economic boom of low unemployment and rising wages. That migrants are drawn to the United States, as they always have been, is because of the opportunities it offers. They are among the most motivated people in the world; migrants can affirm and strengthen essential elements of the American character.

That character is rooted in a belief that the United States is a nation of strivers, standing apart from other countries in its steadfast confidence that hard work and individualism are the way to get ahead. Faced with adversity, Americans rise to the occasion. The journey that migrants make is almost invariably a response to adversity in their homeland, reflecting their longing to reach a place where their hard work and ambition will be rewarded. They arrive already imbued with the traits that are understood as elemental to being an American.

 Yet worries about these migrants often centers on the possibility that they will somehow alter or undermine the American character — that these are destitute people who make life worse for Americans. But these are not tired, poor, huddled masses; some financial means is required to make the long trip the United States. Whether they come in a caravan seeking asylum, by foot across the Sonoran desert to do manual labor, or by airplane on their way to study in U.S. universities or to work in high-tech jobs, they share an energy and motivation that sets them apart from those who don’t migrate. That distinguishing characteristic is what academics call self-selection. It’s easy to overlook character self-selection when so much of the debate about immigration centers on more conventional indicators of selection, such as education level.

Across two centuries, successive waves of immigrants to America, self-selected for character, built the contemporary nation of strivers. Historically, there was no border wall and no border patrol. But there were the Atlantic and Pacific oceans, and crossing them could be deadly.

For the Irish who escaped the potato famine, it was not unusual for 30 percent of the migrant passengers to lose their lives aboard disease-ridden boats known as coffin ships.

At the end of the 19th and beginning of the 20th centuries, millions of Southern and Eastern European immigrants made a two-week journey across the Atlantic knowing, if they arrived safely, they would land in a place that regarded them as unfit to be Americans.

Chinese and Japanese immigrants were met with even more hostility. Designated legally nonwhite, they were ineligible for citizenship.  

In the modern era, many migrants eagerly seeking opportunity and freedom don’t have to risk a deadly ocean journey, but their travel across lands fraught with danger demonstrates a bravery and ambition that is no less impressive. Between October 1999 and April 2018, The Post recently reported, more than 3,000 migrants died in the vast desert region in the Southwest. Families, now mostly from Central America, sometimes walk hundreds of miles through a gauntlet of extortion, rape and humiliation only to have their children taken by U.S. authorities and placed in detention centers after arriving.

The United States, like any sovereign country, has the right to choose who to let in and who to turn away. It would be lamentable if the decisions were skewed by the demonization of these migrants or by a fundamental misunderstanding of their motivations. Most migrants arrive equipped with the determination and eagerness for hard work that will only add to America’s abundance.

Tomás R. Jiménez is an associate professor of sociology and comparative studies in race and ethnicity at Stanford University and the author of “The Other Side of Assimilation: How Immigrants Are Changing American Life.”