The White House is giving foreign policy types and regular humans all kinds of things to worry about. There’s North Korea, of course, and the very real possibility of nuclear war. There’s the ambush and death of four American troops in Niger amid some pretty questionable circumstances. There’s the deliberate sabotage of global action on climate change. There’s inflammatory statements about terrorism, refugees and immigration. There’s the decimation of the State Department and American diplomatic expertise. I could go on.

Some American foreign policy pundits, though, are busy wringing their hands about something else: Trump’s erosion of American “credibility” and his total disregard for this seemingly central aspect of US foreign policy.

As Trump, amongst other things, threatens to decertify the Iran deal, withdraws from UNESCO and tries to provoke “Little Rocket Man”, the editorial board of The New York Times frets that Trump “places little or no value on the idea that honoring national commitments safeguards confidence in America’s word”. The President, they write, “erodes American credibility”. Decertifying the Iran deal, the Washington Post agreed, “would put our credibility and relationship at risk”. Hillary Clinton also weighed in, arguing that, “We have different presidents, and this particular president is, I think, upending the kind of trust and credibility of the United States’ position and negotiation that is imperative to maintain.”

This nail-biting about the importance of maintaining credibility is not new. As an idea and a justification, it has a long and chequered history that is sometimes farcical and sometimes tragic.

You’d be hard pressed to find a world leader who thought Trump would stand by the words of his predecessors and were unpleasantly surprised when he didn’t. Malcolm Turnbull was worried enough about Trump’s position on the refugee deal he made with Obama to raise it in their first phone call and make a fool of himself over it. Leaders the world over – from Trudeau to Merkel to Pena Nieto – had very little confidence in the credibility of the new president, and they haven’t been afraid to show it.

Those same leaders, and others throughout history, aren’t so naive to think that an agreement they negotiated with the previous administration would necessarily continue under the next. Countries that negotiate with the US do so in the full knowledge that a change in administration might mean a change in policy. History teaches them that positions can change even during the same administration.

Under both Republican and Democratic administrations, the United States has broken international law by invading countries without UN sanction, and refused to participate in bodies like the International Criminal Court. More recently, liberal foreign policy pundits berated Obama for his so-called failure to uphold American credibility when he drew a red line for Syria and then refused — for good reason — to follow through.

Despite these unending blows, American power endures. While they may lament a lack of action somewhere, incompetence here, or belligerence elsewhere, the United States’ allies continue to treat with the super power, even under Trump. Most of the time, it’s because their own perceived or actual economic and security needs demand it. Sometimes, as with Australia, it has become a deeply ingrained habit to follow the United States wherever it should lead, and no matter the consequences.

American foreign policy pundits, then, have little to worry about when it comes to the United States’ ability to dominate the world, credibility or no. What they should be wary of — especially given the alarmingly unhinged current occupant of the White House — is just how tragic and dangerous a role this ill-defined concept they so value can play.

After the death of his beloved predecessor in 1963, president Lyndon B. Johnson inherited a volatile and messy conflict in Vietnam. Determined to honour JFK’s legacy by continuing his policies, worried that Vietnam would prevent him from enacting the domestic reform he so cared about, and terrified of failure, Johnson tortured himself over what do about the “damn little pissant country”.

In July 1965, after he had made the fateful decision to “Americanize” the war, LBJ explained to the American people that they were in Vietnam because “three presidents — Eisenhower, Kennedy and your present President — over 11 years, have committed themselves and promised to help defend this small and valiant nation”.

Johnson was well aware of the quagmire that Vietnam could become. In a telephone conversation with senator Richard Russell the year before, Johnson had lamented “I don’t think the people of this country know much about Vietnam, and I don’t think that they care a hell of a lot less.” The American people might not have “cared”, but it mattered to Johnson all the same. Responding to Russell’s suggestion to “get out”, LBJ asked, “wouldn’t that pretty much fix us in the eyes of the world and make us look mighty bad?”

Vietnam did, in the end, make the US look mighty bad. But it wasn’t because of LBJ’s failure to stand by the nebulous and ill-defined commitments of his predecessors. Foreign policy pundits wringing their hands over Trump and his erosion of American credibility would do well to keep that in mind.