Why did copyright in certain foreign works need to be "restored" under the Uruguay Round Agreements Act?

Question

Quizplus · Accepted Answer

The Answer is Certain works from other countries had fallen into the public domain in the United States because their authors failed to comply with formalities imposed by the United States, such as requiring a notice of copyright or the requirement to renew a copyright registration in a work at the time when the United States required such notice and renewal. Thus, these works were automatically restored.

Why Did Copyright in Certain Foreign Works Need to Be