Why and from when has America imposed visa restrictions on Bangladesh?

On September 22, 2023, the Department of State is taking steps to impose visa restrictions on Bangladeshi individuals responsible for, or complicit in, undermining the democratic election process in Bangladesh. These individuals include members of law enforcement, the ruling party, and the political opposition. The United States is committed to supporting free and fair elections in Bangladesh that are carried out in a peaceful manner.

These persons and members of their immediate family may be found ineligible for entry into the United States. Additional persons found to have been responsible for, or complicit in, undermining the democratic election process in Bangladesh may also be found ineligible for U.S. visas under this policy in the future. This includes current and former Bangladeshi officials, members of opposition and ruling political parties, and members of law enforcement, the judiciary, and security services.

They said, their actions reflect the continued commitment of the United States to supporting Bangladesh’s goal of peacefully holding free and fair national elections, and to support those seeking to advance democracy globally.
https://www.state.gov/taking-steps-to-impose-visa-restrictions-on-individuals-involved-in-undermining-the-democratic-election-process-in-bangladesh/