Biden's assignment to Harris was clear, but apparently you are not understanding what she was actually charged with doing and what she had the power to do.

It was not border security, period. She was not assigned to oversee U.S. border enforcement. Managing the border has always been the job of the Secretary of Homeland Security.

Harris' assignment was to work with Central American countries to address the root causes of migration from those countries, to find out what conditions in those countries were causing so many people to flee to the Southern border.

The key phrase in the headline from your link: "Diplomatic efforts to stem migration"

Of course, Republicans began spinning this at the convention into a lie that she was in charge of border security, that she was somehow supposed to fix the border. They continue to perpetuate that as a talking point against her.