In the US, it’s perfectly legal to stream copyrighted content. There are plenty of legal streaming services for this (e.g. Netflix, Amazon Prime Video, and Disney+). In fact, it’s even legal to watch unlicensed streams of movies, TV shows, and sporting events. However, those hosting illegal streams may be prosecuted for copyright infringement. Furthermore, it’s illegal to download unlicensed content because this involves making a copy of the copyrighted work — only the copyright holder has the right to do this.