"I don't think they realize the role that we play," Elizabeth Shackelford told Christiane Amanpour in an exclusive interview on Thursday -- her first since leaving her job at the US Mission to Somalia last week.
The State Department not only helps shape foreign policy, she said, but gets American civilians out of harm's way overseas.
Without the crucial ranks of experienced foreign service officers -- who are increasingly growing disillusioned with President Donald Trump's distrust in diplomacy -- the American government's ability to "avert disasters" overseas, she said, "is definitely going to be impacted."
Shackelford, who served in South Sudan, Kenya and Poland, was considered by many as a rising star at the State Department.
Her scathing resignation
letter, in which she said Secretary Tillerson should resign if he was unable to recommit to the State Department's mission, was obtained and published the next day by Foreign Policy Magazine
"You have to have resources on the ground," she said. "You can't sweep into a place where you don't have relationships and find a way to problem solve."
Case in point: The American evacuation of citizens from South Sudan when violence broke out in late 2013. Shackelford oversaw that effort, and later earned a department award for her work.
"Our ability to get to the airport, secure space at the airport, secure landing permissions for flights, and to get our people out -- that required relationships. And people who were on the ground were able to call up their contacts and navigate that system," she said.
"You can't do that if you don't have people who have been there, who know the culture, who know the city, who know the country, and who know people on the ground," she added.
'Day trading' diplomacy
Trump, Shackelford said, has an inability to see the bigger picture of diplomacy.
"Right now, I feel like this administration looks at foreign policy, and many things, like day trading."
The President's love for Twitter is no help -- American diplomats the world over, she said, now know that "all of what we've said could be undone unexpectedly by 140 characters."
Nowhere was the President's alleged contempt for diplomacy clearer, she told Amanpour, than when he thanked Russian President Vladimir Putin for expelling hundreds of American diplomats this August, "because we're trying to cut down our payroll."
"We're out there in a lot of very difficult and dangerous places; we're far away from our families; and it's hard work. And to have him thank a foreign president for getting rid of -- I mean, you don't need to hear any more than that than to know that the White House has no appreciation for what we do," she said.
Correction: This story has been updated to reflect the fact that Shackelford worked at the US Mission to Somalia, which has offices in Mogadishu and Nairobi.