The Trump Administration is essentially threatening North Korea now - just 10 days after launching an unprecedented strike against Syria and a few days after dropping an unprecedented bomb in Afghanistan.

And back home, that's likely to give a fair amount of the US population heartburn. About 63 per cent, in fact.

US President Donald Trump's biggest liability on the 2016 campaign trail was almost always his temperament. An October Washington Post-ABC News poll showed 64 per cent overall - and 3 in 10 Republicans - said Trump didn't have the right personality and temperament to be president.

The first three months of the Trump Administration have done nothing to disabuse them of this belief. A new Pew Research Centre poll shows 63 per cent of registered voters say Trump is "too impulsive" in making important decisions. And that includes 30 per cent of Republicans and Republican-leaning independents.

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What's noteworthy here is that the poll was conducted at a time when Trump was doing something on the foreign policy front that met with broad bipartisan applause. The strikes in Syria were launched April 6, and the poll went into the field a day later.

Multiple polls have since shown that a majority supported Trump's decision - as much as 57 per cent in a CBS News poll. But even in that poll, there lingered plenty of uncertainty about Trump's foreign policy and temperament more broadly. Fifty-four per cent of Americans said that they remained "uneasy" about his overall approach to Syria, compared with 41 per cent who expressed confidence.

A Washington Post-ABC News poll, meanwhile, showed faith in Trump remained unchanged - if not decreased. While 25 per cent said the Syria strikes made them more confident in Trump's leadership, 28 per cent said it made them less confident. That's not exactly what you'd expect after he undertook what was, on balance, a popular action.

And the Pew poll spells out that continued scepticism pretty well. There was a slight uptick in the number of Republicans and Republican leaners who say they are "very" confident in Trump to handle an international crisis - from 45 per cent before his presidency to 57 per cent today - but that's still 43 per cent of Republican-leaning voters who don't have that level of faith. And among Democrats, 85 per cent now have no or not a lot of confidence in Trump's ability to handle such crises.

Trump's approval rating appears to have levelled off in the high 30s, perhaps owing in part to his decisive action in Syria. But as Trump pursues a similarly decisive and potentially interventionist policy elsewhere - and potentially in Syria again - there appear to be clear limits to the faith the American people will invest in such efforts.

And the fact that Trump is now engaging - rhetorically, at least - with a country that has nuclear weapons is unlikely to mitigate these long-standing concerns about whether he'll make the right decision when that 3 am phone call arrives.