This is as bad as it sounds. It means that any level of US government, from local police to federal agencies, can find and use anything you do online as evidence against you. Did some search and research on anarchism shortly before a protest where someone ended up vandalizing a shop? The local PD could use that as evidence you’re responsible.
Ill try to find resources on mitigating the effects of this, but for now, assume you literally have an FBI agent watching over your shoulder online.