Yes, and if it weren't for the constant campaigns of voter suppression targeted specifically at their communities, you might be making the point here that you imagine yourself to be.
This comment is why it's important to be more precise than the word "authoritarian." We all live under an "authoritarian regime" to one degree or another.
The problem in this case is that its institutionally racist towards, and extrajudicially assassinates, black people with impunity.
We must be more precise because otherwise it allows _this_ to happen.
Even ignoring voter suppression issues, being in a minority group in a democracy does not preclude authoritarian oppression. This is simple math, known as "tyranny of the majority", and is why the US Constitution is longer than just a paragraph about democratic elections.
I am not aware of facts supporting the claim that african americans live under an authoritarian regime.
I am aware that a number of african americans have been unjustly killed by police. That is a different claim than african americans are systematically oppressed by the US government.
For instance, compare what is happening in the US to a real authoritarian regime such as the USSR. The government made millions of innocent civilians disappear into the gulags en masse. Try to imagine even the hint of due process, let alone rioting and protests, within that regime.
Or compare what is happening here vs what is happening in China. The CCP places millions of Uighurs into concentration camps for no reason. In the US, we have thousands rioting violently in the streets, and I suspect the majority of the rioters will see little to no consequences for their actions.