Earlier quoted context omitted.
Because we benefit disproportionately from world peace, uninterrupted shipping, and the world economy using the U.S. dollar as its reserve currency.
The dollar became the world currency by accident after the OPEC started pricing petroleum in dollars. We're starting to see a slow departure from that. If we did not spend those extra tens of billions per year in projecting power, we could better serve our students, workers, retirees, infrastructure, etc. Instead, they go to ensuring Japan, Korea, Philippines, etc. don't have to spend so much on defense. As China asc…
OPEC was formed on September 14, 1960. The definition of "world currency" is somewhat nebulous, but for the purposes of determining when the "dollar became the world currency", perhaps the best date to use is the Bretton Woods conference, which set up the main international financial system, establishing that everyone would peg their currencies to the US dollar, as well as the existence of the IMF and the World Bank. This was done--on purpose, not "by accident"--in June, 1944, 16 years before OPEC ever existed. The Bretton Woods system itself collapses in the 1970s.