“The consolidation of the states into one vast empire, sure to be aggressive abroad and despotic at home, will be the certain precursor of ruin which has overwhelmed all that preceded it.” Robert E. Lee
At this moment Washington has the better part of a thousand military bases around the world, unnecessary except for the maintenance of empire. America exists in a state of constant war, bombing Afghanistan, Pakistan, Syria, Somalia, recently having destroyed Iraq and Libya. Washington threatens Iran, North Korea, Russia, and China. Its military moves deeper into Africa. Washington sanctions Cuba, Russia, North Korea, and Iran, to no effect. It constantly tries to dominate other nations, for example adding to NATO.
In a confederacy, states would have to approve a war. Few would unless the United States itself were threatened. They might well refuse to pay for wars not in their benefit, or to allow their sons, daughters, and transgenders to be conscripted.
But with a central government, those benefiting from war can concentrate money and influence only on that government. For example, military industry, Israel, big oil, Wall Street. Wars might carry the votes of states with arms factories. Other states would decline.