In America, progressivism is liberalism and liberalism is progressivism. What I mean is that we associate the term liberal with more left-wing economics like welfare programs and union support and the term progressive is associated more with socially liberal positions such as environmental protection and gay rights. Someone like me who would (maybe) be a social-liberal would be referred to as a Progressive. Liberalism tends to be used to describe left-wing populism.
Thanks for the clarification. It just seems that many "Liberal" Democrats are adapting the term when it doesn't ideologically fit them.