US does not import Soviet rifles for its military forces. For the record, since the USSR stopped being an entity in 1991, there is no such thing as new Soviet rifles being produced AT ALL.
There are Russian weapons being made, but none of them are procured by US military.
Now, it is entirely possible that private US citizens want to purchase Soviet area or more recent Russian made guns. Why they do that is entirely their decision.
Edit: Mosin Nagant? Technically, those were never Soviet in the first place, as they were produced before the October revolution, i.e. that the USSR did not exist yet in 1916. And those were Russian design ORDERED to be made in the US *for* the Russian forces, as Russia dd not have enough production facilities to make them all. And after the Bolsheviks took over in 1917, they defaulted on the original contrat, meaning that Westinghouse and Remington were stuck with hundred of thousands rifles which they sold to other governments and agencies, including some US units. Let's be clear about it: this happened one hundred years ago.