Reserve currency status makes increasing money supply easier (the US has run large deficits and monetary expansions with less inflation than peers). "Petrodollars" create persistent demand for USD, independent of US domestic conditions - countries that import oil must earn USD (via exports, borrowing, or reserves) or hold US reserves in advance. Oil exporters, on the other hand, invest surplus dollars into US treasuries. This process absorbs US money creation and lowers US borrowing costs. This is an enormous advantage that the US is likely to lose if it continues on its isolationist course.