Timeline: shortly after _Civil War_.
Black Widow is on the run when her attempt to hide out is broken by the delivery of an unexpected package.
Now she has to get back together with her family (of Soviet spies) to take down the Red Room, responsible for her creation.
The MCU timeline is about to run out for Soviet superspies/supersoldiers.
In our timeline the Soviet Union collapsed in 1991. This movie opens with deep cover spies in Ohio in 1995.
Maybe the USSR lasted a few years longer in the MCU Universe.