I: Why does the US help others by mostly spending money on itself?
Whether one looks at civilian and security-related foreign assistance, the United States mostly helps others by (over)spending money on itself. Here is Justin Sandefur of CGD (emphasis added):
Foreigners don’t receive much of America’s $35 billion annual foreign aid budget, at least not directly. Less than ten percent goes to local charities, companies, or governments in developing countries. Instead, big American aid contracts tend to go to big American companies and non-governmental organizations (NGOs). The biggest beneficiaries—known in Washington as “beltway bandits”—each win hundreds of millions of dollars in federal awards every year.