Every US election matters for the world. This year’s election mattered much more than usual, mainly because there was a possibility that a man, viewed as unfit for the job by many in the US and elsewhere, would seize the most powerful job in the world.

Now that Donald Trump has turned that possibility into a reality, defying all the odds and skepticism, the world must brace for a new US -- the undisputable superpower that possesses unrivaled military and economic might -- under a man who has called for change.

South Korea may have to bear the brunt of the “Trump storm” that will batter the world with increased isolationism and protectionism under his principle of “America First.”

What South Koreans -- especially politicians and government policymakers -- should bear in mind is that unlike the pro-Korean, pro-Asia Hillary Clinton, Trump did not hide his negative view of South Korea.

Based on what Trump said during his presidential campaign, South Korea’s challenges with the new US administration will be on two fronts: security and economy.   

Trump said South Korea -- along with countries such as Japan and Germany -- has been “free riding” on its military alliance with the US.

He made it clear that he would demand countries bear their “fair share” of costs for hosting US forces. If not, he warned, he would bring the American troops home. 

These transactional calculations will certainly weaken the South Korea-US alliance which has been acting as the most powerful deterrence against North Korea and a key stabilizer in Northeast Asia.

For South Korea and the region, changes in the US’ commitment to peace and stability would come at a bad time, as the allies and the international community have to deal with the growing nuclear and missile threats from North Korea.

One imminent challenge will be pushing ahead with the plan to deploy a US missile shield system in South Korea next year.

In light of Trump’s stance, there is a possibility the US might demand Seoul bear the cost for hosting the Terminal High Altitude Area Defense battery here. Or in the worst-case scenario, the US could scrap the plan itself.

On the economic front, Trump also mentioned South Korea as one of the countries that benefit -- one-sidedly -- from free trade with the US. He kept describing the South Korea-US Free Trade Agreement, and other bilateral and multilateral trade schemes, as “disasters” that only deprived Americans of jobs.

Some say that Trump’s pledge to abrogate or renegotiate free trade regimes, including the South Korea-US pact and the North American Free Trade Agreement, may remain an election pledge.

But what is almost certain is that Trump will stick to his protectionist path and it will hurt major exporting countries, including South Korea.

What is more worrisome is that these challenges could not have come at a worse time for South Korea. The government is in limbo because President Park Geun-hye has lost much of her leadership power due to a grave influence peddling scandal involving her longtime friend.

As if to alleviate such concerns, Park held a brief telephone conversation with Trump, in which, Seoul officials said, the president-elect offered a strong US commitment to security of South Korea. 

Nevertheless, it remains to be seen how Trump -- who has never held an elected office -- will follow up on what he said during the campaign. Our wish is that President Trump will be different from the presidential candidate Trump, and that much of what he said during the campaign was mere rhetoric aimed at winning votes.

At any rate, we should be prepared for worst-case scenarios in every aspect of relations with the US. Ending the leadership crisis and restoring domestic political stability is the foremost thing to do to cope with the shock waves coming from across the Pacific.