The French daily Le Figaro described him this week as "a Frenchman in the State Department" and part of a "very transatlantic" core of decision-makers in Washington, alongside Obama's choice for the Pentagon, Chuck Hagel, his pick for the CIA, Jack Brennan, and Treasury chief Jack Lew.
The 69-year-old Massachusetts senator has Old World patrician charm and an education to match, for he went to elite schools in New England and Europe. His father was a diplomat who served in Cold War Berlin, and his Paris-born mother a member of the wealthy Forbes dynasty.
Kerry's first cousin is former French Ecology Minister Brice Lalonde, and they spent summers together playing at his mother's chateau in Brittany.
Kerry speaks French fluently - a quality that neo-conservatives in the bruising Kerry-Bush presidential election contest of 2004 tarred as liberal and borderline unpatriotic.
On the Senate foreign relations committee, Kerry, a decorated Vietnam war veteran who spoke out against that conflict, was a powerful influence, demanding during the heyday of the neo-cons that avenues of diplomacy be exhausted before resorting to arms. He swam against the conservative tide by calling for action on climate change.
And he was instrumental in prodding President Barack Obama out of isolationism in the 2011 Libyan conflict. He co-authored a Senate resolution that backed Europe's support for Libyan rebels and committed US forces to implement a no-fly zone. It was the first time Europeans had struck out on their own in a local crisis, but they found themselves hampered by lack of equipment.
Multilateralism, environmental sensitivity and clout in Washington: all of this presses the right buttons in Europe. On Kerry's watch, the US must negotiate a UN treaty on climate change by the end of 2015 - and then have it approved by the Senate.
"Kerry is an advantage, because he is highly respected in the United States because he is a kind of bipartisan man, and we don't see this type of man any more in Congress," said Hans-Ulrich Klose, chairman of the German-American Parliamentary Group in the Bundestag, the lower house of the German parliament.
"He could be helpful to get majorities for this foreign policy line."
But Klose and others caution that foreign policy will continue to be made by the White House, which under Obama shifted focus from Europe to Asia.
Washington must juggle with the emergence of China as a superpower, rivalries over disputed islands that embroil China and the US allies Japan and South Korea, and the headache of North Korea's nuclear programme.
It means that for dealing with the conflicts on its North Africa doorstep, Europe - itself divided - can expect America to continue to be a reluctant partner, said Bertrand Badie, a professor at the top Paris school for political science, Sciences-Po.
"There's a bit of a feeling [in Washington] that the United States are a bit far from Europe and France in particular. So we shouldn't have any big delusions about what changes might happen with the appointment of Kerry and Hagel."
