Upon his election, President Obama foolishly sent more troops to Afghanistan and renewed the intensity of that war, now in its eleventh year, to no successful effect.
These two wars have been expensive. According to estimates by Joseph Stiglitz and Linda Bilmes, when all costs are counted the Iraq invasion cost US taxpayers $3 trillion dollars. Ditto for the Afghan war. In other words, the two gratuitous wars doubled the US public debt. This is the reason there is no money for Social Security, Medicare, Medicaid, food stamps, the environment, and the social safety net.
Americans got nothing out of the wars, but as the war debt will never be paid off, US citizens and their descendants will have to pay interest on $6,000 billion of war debt in perpetuity.