The United States of America as it existed in Jack’s childhood had a relatively weak Federal government compared to the various State governments that selected its Senators. But the Western Alliance had colonized nearly two dozen star systems before Contact, and America tried to place at least small colonies in each of them. Add in the many, many more colonies started once cheaper and more efficient gravitic hyperspace engines came out, and the federal government had an impressive amount of taxes coming in. Far more than they needed for their regular operations. And the States denied them the option of funding Federal social programs in order to control the population. So the Feds built big beautiful buildings in the District of Columbia, big beautiful buildings in the colonies and territories to administer them, and a big beautiful black navy fleet to fly between every rock that carried an American flag anywhere on it. And that is why the American Federal Navy was one of the largest navies in existence when The War began.