According to the National Congress of American Indians (NCAI), 573 sovereign tribal nations currently have a formal relationship with the United States. Altogether, these tribal governments have jurisdiction over enough land to make Indian Country the fourth largest state in the nation. Tribal goverments are able to pass their own laws, enforce them through police departments and courts, and build their own infrastructure like roads and buildings.
The NCAI states that "...there are several obstacles to tribal self-governance based on three thematic areas that have been identified in recent years: (1) outmoded bureaucratic processes; (2) lack of federal agency coordination; and, (3) regulations and laws that prevent tribal governments from equitable access to federal programs on par with state and local governments".
Click here to read NCAI's full article about Tribal Governance.
Source: National Congress of American Indians