Feist Publication, Inc. v. Rural Telephone Service Co., 499 U.S. 340, 349-50 (1991) (citations omitted) gives the primary purpose of copyright:
The primary objective of copyright is not to reward the labor of authors, but [t]o promote the Progress of Science and useful Arts. To this end, copyright assures authors the right to their original expression, but encourages others to build freely upon the ideas and information conveyed by a work. This result is neither unfair nor unfortunate. It is the means by which copyright advances the progress of science and art.
The first clause above seems to imply that U.S. law does not consider copyright infringement an act of injustice toward the copyright owner.
Which countries do or do not consider copyright infringement theft?