The 158 million people in those states make up the same share of the U.S. population -- 49% -- as the proportion of Syrians that have fled carnage there.
The war in Syria is so hellish and unrelenting that more people have left that country than any other in recent years. One of every five displaced persons in the world is Syrian.
Here's a look at where those Syrians have gone.
Protests against the government in Syria in 2011 soon devolved into chaotic war. The fighting and later rise of ISIS had forced 10.6 million people from home by late 2015 -- about half of Syria's pre-war population.
Most have fled to countries near Syria
Most Syrians who have left their homeland registered as refugees with the United Nations. Three in four Syrian refugees did that in Turkey, Lebanon or Jordan, according to UN figures from February 2016.
More of them have gone to Europe
The number of Syrians seeking safety in Europe more than doubled from 2014 to 2015. Many left Turkey and other countries for Europe to ask for asylum, a status that allows someone to live and work legally in another country.
They're not the only ones
Worldwide, 59.5 million people are on the move as refugees or displaced people
within their home countries. That population would be enough to make them citizens of the world's 24th biggest country.
Humanity has never seen such displacement. Ever.
"Wars, conflict and persecution have forced more people than at any other time since records began to flee their homes and seek refuge and safety elsewhere," the United Nations said in June.
At least 15 wars and conflicts are to blame -- in Africa, the Mideast and Asia.
Some destinations are more popular than others
Three out of five Syrians seeking asylum in Europe are in Germany, Sweden or Serbia. Relatively large numbers of Syrians also have sought asylum in Hungary, Austria, Bulgaria, the Netherlands and Denmark.
Among the European countries receiving the fewest asylum requests are Latvia, Estonia, Lithuania, Slovakia and Iceland.
Hardly any have found refuge in wealthy Gulf states
Gulf states such as Saudi Arabia, Qatar, Kuwait and Bahrain have been criticized for resettling no Syrian refugees despite similarities of language, religion and culture.
Human rights groups say the Gulf states, their wealth reflected in skyscrapers and upscale shopping malls, have plenty of resources to resettle Syrian refugees. Some in the Gulf states point out that they have contributed tens of millions of dollars in humanitarian relief for displaced Syrians.
The United Arab Emirates, on the other hand, has been welcoming, receiving and extending residency permits to more than 100,000 Syrian nationals since 2011, a UAE government source told CNN.
The United States is resettling more Syrian refugees
The United States has resettled 1,500 Syrian refugees since the start of the conflict in 2011, the vast majority of them this year.
That amounts to about 0.03% of Syria's 4.1 million refugees.
Here's a breakdown: 23 in 2011, 41 in 2012, 45 in 2013, 249 in 2014 and 1,199 so far this fiscal year, which ends September 30, according to the State Department.
About 300 more refugees are expected to be admitted by the end of the month, according to U.S. officials.
In the face of growing questions about such small numbers, President Barack Obama ordered his administration to "scale up" the number of Syrian refugees -- at least 10,000 in the next fiscal year.