Is the Library of Congress really a national library?

From "Jefferson's Legacy - A Brief History of the Library of Congress" by John Y. Cole

Since its creation, the Library of Congress has been part of the legislative branch of the American government, and even though it is recognized as the de facto national library of the United States, it does not have that official designation. Nevertheless, it performs those functions performed by national libraries elsewhere and has become a symbol of American democracy and faith in the power of learning.
(A warning about that document, it appears to be fact-based propaganda and contains very few facts that shed the Library of Congress in anything but a positive light.)