Forum Moderators: not2easy
If I understand the website correctly Copyright.gov does not provide direct, online access to the copyrighted material. If it did it likely would be working as a second Library of Congress. Instead, you can simply do up for the existence of copyrighted materials pursuant to what they choose to catalog: Author's name, date, etc. (See link above.)
You may have to write and pay a fee for the Copyright Office to make you a copy.