In some ways, the Atlantic Ocean seems unusually wide at the moment.

Polls by the Pew Research Center show that western Europeans take an increasingly dim view of the United States, and not just its president. On the other side of the ocean, conservatives think that a clinching argument against universal health care is to call it European. Yet in other, more intimate, ways the two continents appear to be converging. U.S. families are increasingly hard to distinguish from European ones.

Soon after the Great Recession hit the U.S., in 2007, the birthrate began to fall. Many people lost their jobs or their homes. But in the past few years the economy has bounced back — yet births continue to drop. The total U.S. fertility rate, which can be thought of as the number of children the average woman will bear, has fallen from 2.12 to 1.77. It is now almost exactly the same as England’s rate, and well below that of France.

Although getting into Harvard will be a little easier as a result, this trend is bad for the U.S. in the long run. A smaller working-age population makes Social Security less affordable and means the national debt is carried on fewer shoulders.

The U.S. could admit more immigrants to compensate, but politicians seem loath to allow that. The baby bust also strikes a blow to U.S. exceptionalism. Until recently, it looked as if pronatalist policies such as generous parental leave and subsidized nurseries could be left to those godless Europeans. In the U.S., faith and family values would ensure a good supply of babies.

What changed? One possibility is that the drop is little more than a mathematical quirk. The total fertility rate is calculated by adding up the proportions of women in each year of life who had a baby in the previous year. Suppose that all U.S. women have exactly two children. If a cohort of women move to have those children later, the fertility rate will temporarily fall below two. This happened in the late 1970s, when the rate dipped to 1.74 before recovering.

To some extent, history is probably repeating itself. In 2017 the mean age of a first-time mother was 27, up from 25 in 2007. The teenage birthrate has halved in the past 10 years — something that Power to Decide, a campaign group, attributes to less sex and better contraception. Colleen Murray, its senior science officer, said the Affordable Care Act has made long-acting contraceptives like IUDs available to more young women.

The trend of Americans giving birth at ever older ages could run for a while. In Europe, a women’s mean age at first birth is 29. In Japan it is 31.

Still, comparisons with Europe and Japan are not exactly reassuring — both countries have smaller families than the U.S. And with every passing year the drop in U.S. fertility seems less temporary. Some data suggest that people have come to desire small families. The National Survey of Family Growth shows that 48 percent of U.S. women with one child expect not to have a second.

Some religious conservatives fear that a broad shift is underway. According to Gallup, a pollster, the share of Americans who never go to church has risen from 10 to 27 percent since 2000. That could be connected to falling fertility. But it is hard to disentangle cause from effect.

What is clearer is that the U.S. fertility rate is being pulled down by two groups of people: Latinos and urbanites. Latino women still have more children, beginning at a younger age, than non-Latino whites, blacks or Asians. But their fertility rate is falling exceptionally quickly. Between 2007 and 2017 it dropped from three to two, pulling down the national average.

William Frey, a demographer at the Brookings Institution, points out that the recession hit them hard. Many Latinos worked in the construction business, which collapsed, and lost their homes to foreclosure. Latinos are also increasingly American. Two-thirds were born in the country, and the proportion is rising. They have probably adopted American small-family norms.

The fertility rate has fallen more sharply in large cities than in smaller cities or rural areas. Rents and prices have soared, making it harder to afford an extra bedroom. Lots of properties are being built in city centers — but many of these are tiny flats in towers. In 2006, only 27 percent of newly-completed apartments had fewer than two bedrooms. In 2017, fully 48 percent did.

Nir Shoshani of NR Investments, a property developer in Miami, said some of this change is driven by demography. People are staying single and childless for longer, so there is more demand for small flats. But the towers are also rising because politicians and officials want them to rise. As in other cities, Miami’s zoning laws have changed to favor little boxes. A recent reform allows builders to create homes of just 275 square feet.

It is possible that cities like Miami are not only accommodating the growing ranks of single and childless people, but are creating more of them. Hill Kulu, a demographer at the University of St. Andrews in Scotland, has found that in England and Finland suburbanites and small-town-dwellers have more children than you would expect from looking at other aspects of their lives. It is almost as if extra bedrooms and child-friendly neighborhoods make children.

Perhaps the U.S. family is becoming more European because its cities are looking a little denser and a little less suburban — that is, a little more European.