The country’s 150-year-old right of citizenship to every person upon birth on U.S. soil has become the latest test question for GOP presidential candidates, with Donald Trump and Ben Carson coming out strongly in favor of ending the practice.

In an appearance on CNN’s State of the Union, conservative pundit S.E. Cupp suggested the United States’ law makes it an outlier on the issue compared to the rest of the world.

"There are actually only 30 countries that practice birthright citizenship," she said on the Aug. 23, 2015, show, "making the U.S. kind of an anomaly."

We wanted to see if the United States is one of 30 countries in the world to offer automatic citizenship to anyone born on its soil.

We reached out to Cupp through her publicist but did not hear back.

Around the world

The legal term for birthright citizenship is jus soli, or "right of the soil." It’s different from the term jus sanguinis, or "right of blood," referring to laws which rely on a person’s heritage to determine his or her citizenship status.

Birthright citizenship in the United States was first made law by the 14th Amendment of the Constitution, primarily to grant legal status to emancipated slaves. The amendment stipulates that "all persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside." The Supreme Court solidified the Constitution’s authority on this issue in 1898 by ruling that citizenship is a right offered unconditionally to all born on U.S. soil.

How many other countries share this guarantee? NumbersUSA , a group that favors reduced immigration, compiled a list that shows 33 nations grant citizenship to anyone born within their borders.

The United States is joined by Brazil, Argentina and Mexico, along with nearly every country in Central and South America. The United States and Canada are the only two "developed" countries, as defined by the International Monetary Fund, that still have unrestricted birthright citizenship laws.

A closer look at the list shows an interesting trend: Countries that offer birthright citizenship are located almost exclusively in the Western Hemisphere. No country in Europe or East Asia, for example, has a similar citizenship policy.

So why does birthright citizenship literally divide the world?

One explanation may be colonialism, said John Skrentny, a sociologist at the University of California, San Diego. As European countries colonized the Americas, Skrentny said, many created lenient naturalization laws in order to grow and overpower native populations.

"Getting people to move in was a good way to establish authority," he said.

This method of citizenship hasn’t changed that much in the centuries since. Many of the birthright laws in South America have remained due to low immigration numbers , he said.

The United States, however, has retained its birthright citizenship laws, even as it admits around 1 million people every year through its legal immigration system. Canada, which also has a birthright citizenship law, still takes in around 250,000 legal immigrants a year.

Conversely, in Europe, many countries have modified their requirements for citizenship in recent years. Ireland got rid of its birthright citizenship law in 2005, and France did away with its own in 1993.

Many European countries still maintain a version of birthright citizenship, however. In Germany and the United Kingdom, citizenship is now automatically granted to a person if at least one of his or her parents is a citizen or permanent resident.

Our ruling

Cupp said, "There are actually only 30 countries that practice birthright citizenship, making the U.S. kind of an anomaly."

The United States is one of 33 countries around the world that offer citizenship to every person born on their soil. Among those 33, the United States admits the highest number of immigrants per year. In contrast, most other developed countries have added more requirements for citizenship. This makes the United States somewhat of an outlier on the issue.

We rate Cupp’s statement True.

Clarification: Among the 33 countries with birthright citizenship, the United States admits the highest number of immigrants per year. An earlier version of this story was unclear.