The Pentagon had been monitoring the balloon since it left China, and it had previous opportunities to shoot it down while it was over U.S. territorial waters when it crossed over the Aleutian Islands. The Biden administration most certainly knew what it was and where it might go, and the opportunity to shoot it down safely over the water was not taken
https://pjmedia.com/news-and-politics/matt-margolis/2023/02/05/bidens-story-about-the-spy-balloon-doesnt-add-up-heres-what-most-likely-happened-n1668015