Stop me if you've heard this one before.

What do you call someone who speaks two languages? Bilingual. What do you call someone who only speaks one language? American.

That old joke highlights America's reputation for being largely monolingual. In comparison to places like, say, the entire European Union, where over half the people can speak at least two languages, the U.S. has got some linguistic catching up to do.

In particular, no U.S. presidents after Franklin D. Roosevelt (1882-1945) have been bilingual. Brought up in a wealthy home with an evolving door of governesses, FDR was the last U.S. president who was fluent in a language besides English — he spoke French and German.

After FDR came decades of monolingual leaders. A number of presidents have been conversational in other languages: Jimmy Carter speaks conversational Spanish, as do George W. Bush and Barack Obama (who also speaks some Bahasa Indonesian).

Bill Clinton studied German in college, though he isn't fluent. That's a far cry from the varied bilingual and multilingual leaders of the past. Early presidents like Thomas Jefferson and John Quincy Adams were fluent in at least two other languages (Jefferson dominated, speaking French, Italian and Latin). Martin Van Buren's native language was Dutch. Herbert Hoover was fluent in Chinese.

After FDR, the fluency comes to a halt. Why the dramatic downturn?

"Before FDR, you had a number of patrician presidents," author and historian Dr. Gordon Chang tells Mashable. "People with high levels of education are more likely to have fluency in a second language." Though there were also presidents from "humble origins," such as Abraham Lincoln, the White House was often home to men with wealthier roots.

However, that makes it harder to explain presidents like John F. Kennedy, who had an elite upbringing, but wasn't fluent in any other languages. Dr. Larry Sabato, the director at the University of Virginia's Center for Politics, attributes this to a lack of focus on foreign languages in the U.S. at the time.

"For much of modern American history, language study was not stressed or even encouraged in our schools, or our secondary schools or colleges," Dr. Sabato tells Mashable.

In 2010, U.S. Secretary of Education Arne Duncan spoke about America's "language gap" at the Foreign Language Summit, saying "...the United States may be the only nation in the world where it is possible to complete high school and college without any foreign language study." He also shared this statistic about our "spotty" U.S. foreign language system: Just 18% of Americans speak another language besides English, compared to 53% of Europeans who speak more than one language.

When did this decline begin? Dr. Chang has a theory.

"The United States became very powerful after the second World War," he says. "Americans didn’t need to learn another language — other countries needed to learn English."

"You're either with us, or against us."

It should be noted, numerous presidential candidates have been at least bilingual. John Kerry, who ran against George W. Bush in 2004, is fluent in French. Jon Huntsman, who ran in 2012, has a healthy grasp on Chinese (though his claims of fluency seem to be overinflated). Mitt Romney, who ran most recently in 2012, is fluent in French. Jeb Bush (who is "actively exploring" a 2016 run) is fluent in Spanish.

However, in recent years bilingual candidates have been attacked for their linguistic capabilities in the past, particularly by the Republican party. In 2011, Romney was attacked for his skill, accused of being too French by detractors; an attack ad was created based on his French-speaking abilities alone. The same thing happened to John Kerry in 2004.

"There’s always a hidden American fear about the 'Manchurian candidate' — the idea that someone not genuinely American would become president," Dr. Sabato says.

That type of fear isn't just limited to the U.S. — numerous world leaders have declined to speak foreign languages, particularly English. This past June, Indian prime minister Narendra Modi, who speaks English, decided he will only speak Hindi when meeting with global leaders.

As Washington Post's Adam Taylor points out, Modi isn't doing this to be difficult — he's doing it to showcase pride for his country, especially because speaking English has caused a divide between non-English speakers. In addition, India's history of English colonialism might also lend itself to Modi's decision, Dr. Chang notes.

There's also one more, well, strategic reason politicians pick their language first in global meetings.

"If questions are translated into their own language, it gives them more time to think," Dr. Chang explains. "The president or prime minister will completely understand the question...and on the other side, translators get to clean up answers."

A future asset for a connected world.

"It really is the era of the global community," Dr. Sabato says.

Since Secretary Duncan's 2010 speech about the lack of foreign language speakers, the Census Bureau has found that an additional 2.2 million people report speaking a foreign language as of 2013. There's also been a rapid increase, starting in the mid-1980s, of college students who study abroad, writes David Northrup, author of How English Became the Global Language. This has helped "stem the decline of foreign language study" in the U.S., he writes.

It's a positive sign, though it's a small achievement in the scheme of things. The NAFSA found that in the 2012-2013 school year, about 289,408 students studied abroad, which only represents about 1% of all U.S. students enrolled in higher education.

However, America's greater landscape is changing. By 2050, immigrants will make up 37% of the population, the highest in history according to a Pew Research study. The Hispanic population will make up 28% of the country, up tremendously from 2010's 16%. Politicians recognize the importance of capturing those votes. In 2012, President Obama nabbed more than 70% of the Hispanic vote, as well as the Asian-American vote.

Jeb Bush, in his "active" exploration of a 2016 bid, has basically been flaunting his Spanish-speaking skills, a big no-no from the last election cycle.

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"The Republican Party, they realize Hispanics are a very important voting block and are going to determine elections in the future," Dr. Chang says. He anticipates more language-flaunting in the future.

"It’s inevitable — in the end, politicians do reflect their constituency," Dr. Sabato notes.

Outside of the White House, that constituency is rapidly evolving.