A number of high-profile figures at the Department of Homeland Security have left their posts in the past week: Secretary Kirstjen Nielsen resigned Sunday night, President Donald Trump dismissed the head of the Secret Service Tuesday, and the acting DHS deputy resigned Wednesday. The shake-ups are reportedly motivated by the president's desire to get tougher on immigration.

Homeland security expert Juliette Kayyem said the president's "myopic" focus on the border is leaving the United States vulnerable to other threats. Kayyem is on the faculty of Harvard’s Kennedy School and a CNN analyst.

"We've got a big country here with a lot of vulnerabilities," Kayyem explained.

"Our myopia on the border, as compared to cyber threats and terrorism and right-wing terrorism, and climate change, and hurricane season coming upon us, and pandemics like the measles outbreak that is causing an emergency declaration in New York City — those are also homeland security challenges," she said.

"The president seems either unconvinced that they are challenges or uninterested," Kayyem said.