The Daily Northwestern, a daily newspaper published by students at Northwestern University, has this op-ed advocating that the U.S. use proportional representation for congressional elections. The paper is considered one of the best student newspapers in the nation, and it also serves as the only daily newspaper for Evanston, Illinois.
The author only presents one type of proportional representation. Also he says constitutions would need to be changed. It may be true that some state constitutions would need amendments, but nothing in the U.S. Constitution blocks proportional representation for Congress. States are free, under the Constitution, to elect members of Congress any way they wish, as long as they are chosen by popular vote. However, a federal law mandating single-member U.S. House districts would need to be changed. A bill will be introduced in Congress to repeal that law.