The point being made by Nursie above is simply that what you are calling "Progressive left" in the USofA is a position largely seen as centralist in other parts

The point being made by Nursie above is simply that what you are calling "Progressive left" in the USofA is a position largely seen as centralist in other parts of the world. By stating tht there is "effectively no political left wing in America" they are asserting that the furtherest political left position held in the USofA is a centralist one called "Progressive left" there in the US.