Answer:
When a problem arises with the Navajo nation, whose territory crosses state boundaries, the Federal Bureau of Indian Affairs would help.
The Bureau of Indian Affairs is a federal government agency charged with managing the native territories and the resources that are granted to these groups, whose main officer is Bryan C. RIce. It is an organism dependent on the Department of the Interior, and is in charge of procuring through the administration of the territory and the resources the well-being of the natives lodged in lands granted by the federal government. Therefore, in the event of structural problems that transcend the Navajo Nation's sphere of influence, this agency would be the first to act.