This is the statement from the US Embassy on the issue
"In response to the April 2019 Presidential Memorandum on Combating High Nonimmigrant Overstay Rates, the Department and our embassies and consulates overseas conducted an in-depth analysis to identify and address root causes of overstays.
Among other efforts to address this challenge, the State Department is considering additional steps to address overstays, including piloting a limited visa bonds program to test, in coordination with the Department of Homeland Security (DHS), the operational feasibility of posting, processing, and discharging visa bonds as means to ensure the timely departure from the United States of certain travelers.
Accordingly, the State Department will begin a limited six-month visa bond pilot program beginning on December 24, 2020.
We are committed to combating visa overstays and making sure travelers to the United States respect our laws.
The implementation of this pilot builds on our engagement with foreign governments in recent years and will ensure continued progress to reduce overstay rates.
*Nigeria is not included in this six months pilot program."
Source: US Embassy