What is the significance of foreign affairs to the United States at the time of its founding versus today?

Foreign policy is important because it determines the state of relationships between countries and guides the diplomats in negotiations. If a country is too aggressive and refuses to take into the legitimate interests of other countries, it may face a push back or even an armed conflict.

The answer is:

The significance of foreign affairs of the United States of America has changed a lot from the time of its founding until present day. Foreign policy is the State's interactions with other nations and how it sets standards of interaction for its corporations, organizations and citizens of the country.

The main trend regarding the significance of U. S. foreign affairs since the American Revolution is the shift from non-interventionist before and after World War I, to its growth as an only world power and globe hegemony after World War II.