While law enforcement violating civil rights is sadly not new, Trump appears to be trying to do something novel in this country: establishing a force like interior ministries in other countries. The United States has a Department of the Interior, but it is unlike most agencies with that name around the world. Here, it oversees units like the National Park Service, the Bureau of Indian Affairs, and the U.S Geological Survey. But in many countries, its role is much broader and powerful powerful: Its role is to oversee the interior of the country.
One common tool for an interior ministry is a national police force. That can be a dangerous tool, because an armed, national police force at the disposal of the central government has a tendency to be misused. A repressive regime that is in danger, or simply faced with protests it finds troublesome, can use the national police to crack down, turning the force into an agency that protects the rulers, rather than one that defends the rule of law. Even in more democratic countries, a national police force can be a threat. In early post-Franco Spain, the Guardia Civil was a hotbed of fascist irredentism.
The United States has never had a national police force like this, for reasons that emanate from the country’s founding. While the federal government has grown ever-stronger since independence, the federalism embedded in the American system militated against a national police force. (Even state police were slow to emerge.) The Founders were wary of establishing any permanent, armed force under the control of the federal government, even warning against a standing army.