Trump's immigration ban doesn't include the country most of the 9/11 hijackers came from

President Donald Trump's executive order barring immigrants from seven Muslim-majority countries from entering the US doesn't include the country that most of the 9/11 attackers came from - Saudi Arabia.

The executive order bars citizens Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen from traveling to the US. Trump adviser Kellyanne Conway said over the weekend that the order is "a ban on prospective travel from countries ... that have a recent history of training and exporting and harboring terrorists."

Trump also cited the September 11, 2001 terrorist attacks on New York City and Washington, DC directly several times in his executive order.

"The visa-issuance process plays a crucial role in detecting individuals with terrorist ties and stopping them from entering the United States," the order stated." Perhaps in no instance was that more apparent than the terrorist attacks of September 11, 2001, when State Department policy prevented consular officers from properly scrutinizing the visa applications of several of the 19 foreign nationals who went on to murder nearly 3,000 Americans."

Fifteen of those 19 foreign nationals were from Saudi Arabia. Osama bin Laden himself was born in Saudi Arabia, and his family had strong connections to the Saudi royal family. And yet Trump's executive order does not apply to foreigners from that country.

Saudi Arabia has a long history of exporting Wahaabism, a strict strain of Islam that has been blamed for fueling extremism around the world.

Farah Pandith, America's first special representative to Muslim communities at the State Department, wrote for The New York Times that in each of the 80 countries she visited between 2009 and 2014, "the Wahhabi influence was an insidious presence, changing the local sense of identity; displacing historic, culturally vibrant forms of Islamic practice; and pulling along individuals who were either paid to follow their rules or who became on their own custodians of the Wahhabi world view."

Pandith continued: "Funding all this was Saudi money, which paid for things like the textbooks, mosques, TV stations and the training of Imams." She called on the countries around the world to "reject free Saudi textbooks and translations that are filled with hate" and "expose the Saudi financing of extremist groups masquerading as cultural exchanges and 'charity' organizations."

Trump himself called Saudi Arabia the "world's biggest funder of terrorism" in 2011.

On "Meet the Press" in 2015, Chuck Todd asked Trump why the US should have diplomatic relations with Saudi Arabia if the country funds terrorism.

"The primary reason we are with Saudi Arabia is because we need the oil," Trump said. "Now, we don't need the oil so much."

He continued: "Like it or don't like it, people have backed Saudi Arabia. What I really mind though is we back it at tremendous expense. We get nothing for it."

Saudi Arabia has been a major US ally for decades. From 2011 to 2015, Saudi Arabia has been the top destination for US arms exports.

Trump also has a personal financial link to Saudi Arabia, as The New York Times noted. The Trump Organization registered eight companies in Saudi Arabia in 2015.