There are a few reasons that could be happening. The first might be a widespread glitch that has happened in the past and that as of this writing, is affecting many users all across the United States. While this error could be taking place for a bunch of different reasons, the most likely one is a server timeout or general issue.

Localized servers that house, send, and receive data might be malfunctioning or could be in need of maintenance. Since Instagram is a massive online undertaking, specific types of content can be "blacked out" for users, and other features may be restricted if just one of the servers goes down.