Progressives aren't even left wing, let alone communist, and they aren't at all opposed to US imperialism. They are fakers whose role is to sheepdog real left-tending voters into irrelevance.
The southern primaries are usually their curtain call, if they survive that then the big-urban states like New York and California inevitably do them in. People forget what the maps looked like for Sanders in 2016 - winning the rural areas and losing very badly in places like New York City and Southern California. Couldn't even sway Brooklyn. Those wealthy urbanites are the Dem core and they will get what they want.