It is symbolic and poignant that the election of Mr Donald Trump was confirmed on the morning of Nov 9, 27 years to the day after the fall of the Berlin Wall.
That was a moment of triumph for United States leadership - and ushered in a period of optimism and expansion for liberal and democratic ideas around the world. That era has been definitively ended by Mr Trump's victory.
The electoral triumph of a race-baiting demagogue represents a profound blow to the prestige of US democracy - and thus to the cause of democracy around the world, which America has championed, on and off, since 1945.
The most eloquent and moving statement of that American commitment was made by John F. Kennedy in 1961: "Let every nation know, whether it wishes us well or ill, that we shall pay any price, bear any burden, meet any hardship, support any friend, oppose any foe, to assure the survival and the success of liberty."
The generosity, breadth and eloquence of Kennedy's vision makes a sad contrast with the pinched nationalism of Mr Trump's proclamation that "our plan will put America first. Americanism, not globalism, will be our credo".
The difference between these two visions is profound and ominous. It was not just idealism that led America's post-war generation to commit to the protection of liberty around the world. As Kennedy observed, his generation was "tempered by war, disciplined by a hard and bitter peace". They make a stark contrast with the generation who have voted for Mr Trump - fattened by fast food and infantilised by reality television.
The Kennedy generation had learnt bitter lessons from the Great Depression and World War II. They knew that "America First" policies - those that sought to isolate the US from the problems of the wider world - had ultimately led to economic and political catastrophe. So after 1945, a new generation of US leaders, both Republicans and Democrats, built an economic and security architecture for the world - based around US leadership and international institutions and alliances such as Nato, the United Nations and the World Bank.
Mr Trump has forgotten these lessons drawn from the experience of the 1930s, if he ever knew them. He appears to have even more contempt for international bodies than for the institutions of America itself.
His proposed policies threaten to take an axe to the liberal world order that the US has supported and sustained for many decades. In particular, he has challenged two of the main bipartisan principles that underpin America's approach to the world. The first is support for an open, international trading system. The second is the commitment to the US-led alliances that underpin global security.
Mr Trump is the first avowed protectionist to be elected US president since before World War II. He has promised to renegotiate America's "terrible" trade deals, such as the North American Free Trade Agreement, and threatened to pull the US out of the World Trade Organisation. He has also mooted tariffs as high as 45 per cent on Chinese goods. If Mr Trump were to follow through on these threats, he would spark a global trade war and could well plunge the world into recession - similar to the depression of the 1930s, which was greatly deepened by America's embrace of protectionism.
Mr Trump's effect on the global security system could be just as dramatic. The President-elect has questioned whether the US will honour its security commitments to Nato allies and to Japan and South Korea - unless these countries pay more for their defence.
American annoyance at "free-riding" by its allies is a bipartisan concern. What is new is Mr Trump's overt questioning of the idea that the US will defend its allies from a military attack - come what may.
This equivocation - combined with Mr Trump's open admiration for Russian President Vladimir Putin - will raise fears that the US will not oppose renewed Russian aggression in Ukraine or Eastern Europe. America's Asian allies - in particular, Japan and South Korea - also fear that Mr Trump's "America First" policies could extend to accepting a Chinese sphere of influence in East Asia.
The temptations of an "America First" policy are understandable for a country that is tired of wars in the Middle East - and that has apparently been persuaded that international trade is the source of its domestic economic problems. The US has a huge internal market to sustain its economy and two vast oceans to protect its security. In time, however, the US is likely to become a poorer and meaner place if it disengages from the rest of the world. And, as in the 1930s, the security and prosperity of America itself is also ultimately likely to be threatened by a collapse of international trade and a resurgence of authoritarian aggression.
But all that lies in the future and in the realm of conjecture. In the present, America and the world face a simple and depressing truth.
The American presidency - an office once occupied by giants such as Lincoln, Roosevelt and Kennedy - has been captured by a shallow huckster.
Mr Trump has promised to "make America great again". But his ascension to the presidency is actually a terrible sign of national decadence and decline.
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