Oh please, take to your fainting couch and relax:
President Donald Trump’s emergent foreign policy agenda is a repudiation of the largely bipartisan consensus that has dominated U.S. grand strategy since the end of World War Two: that the U.S. should seek and maintain primacy in international affairs. Even more worrying, Trump’s approach also has the potential to accelerate the end of the ‘American era’ in international affairs.
One, the author over-states the notion that "the world" accepted our design of the post-World War II order. The Soviet bloc never accepted that and post-civil war China soon rejected it. India wasn't that wild about it either, in many ways.
Two, the decline of American power from peaks has happened twice since World War II and shouldn't be a matter of too much concern. In 1945 we stood astride the world like a Colossus because all our enemies were smashed and even our allies were exhausted.
As the world recovered, our relative strength naturally declined. In the 1970s, people worried (and some in the West to their shame, hoped) that the American century was over and that the Soviets would assume the mantle of dominant power.
Then the Soviet bloc collapsed and once again America was the only super power still standing.
Russia is recovering, China and India are advancing, and even Japan is rearming along with South Korea as a significant player. So our relative power will continue to decline.
But never forget that our deployable power will always be far greater allowing America to intervene to tip a balance. European states, Japan, Russia, China, and India all have major military threats near them that absorb most of their military power.
America, by contrast, has either relatively weak friends as neighbors (Mexico and Canada) or weak foes (Cuba and Venezuela) nearby. Even as our relative power declines from that Soviet collapse peak, as other states rise America will retain significantly more free power to project abroad.
And Trump with Congressional support is committed to rebuilding American military strength by improving readiness which has lagged in the last 8 years and by reversing the decline in numbers in the forces.
And he wants to repair our economy that still limps along.
I know Trump isn't popular abroad. But assuming that all things bad must follow from your own Trump Hysteria Condition panic attacks isn't a reality-based analysis.
People keep claiming America's twilight is imminent and it doesn't seem to ever arrive.
America will be there for our ally of long standing, Australia. Period.
UPDATE: America's military presence in northern Australia, where it is close enough to operate in the Indian Ocean or South China Sea but far enough away from China to avoid being an easy target, continues to grow.