Mass surveillance in the United States basically means that the government is watching or keeping an eye on what people in the US are doing. This means that the US government can use special technology to track what people do online and on their phones, and even in their homes. They may look at things like emails, text messages, phone calls, social media posts, and other online activities to help them understand what is going on in the country. The government is able to do this because they have access to very powerful computers that can take this data and look for patterns or signs of wrongdoing. This means that they can potentially detect illegal activities or suspicious behavior before it happens. Even though this is done to help keep the country safe, it can also invade people's privacy.