Even if you don't agree with it, I ask that you look into it since you don't even know what liberalism is (individualism, modernism, subjectivism, capitalism, and a lot more). At least, it might allow you to better understand why it is a heresy. Feser has a title called Locke that goes into it. There's also Unintended Reformation that shows that liberalism has roots in the Reformation. There is a book called the Case Against the Modern World that is interesting and provide some sources. I disagree with a lot of the book as it thinks that the whole of the traditional thought held in the Middle Ages was good and we cannot take anything from the Modern Era. In terms of capitalism, there are some papal encyclicals from Leo XIII, but I also recommend looking into leftist literature as Catholicism didn't put much energy into critiquing the economic system.