Final answer:
The ability to control borders is an example of a nation's sovereignty, reflecting its autonomous authority and influence in international relations.
Step-by-step explanation:
The ability to control borders would be an example of a nation's sovereignty. Sovereignty refers to the full right and power of a governing body to govern itself without any interference from outside sources or bodies. The United States' control over its borders is a manifestation of its sovereignty, which is an essential aspect of its national identity and political authority. A country's ability to manage its own affairs is closely related to its power to control territory and resources, as well as to influence international political relations. This is evident in the United States' ability to negotiate trade agreements like NAFTA, where it effectively manages its economic interactions with other nations to maintain a position of strength.