On Sunday, as more than a million marchers took to the Paris streets and 44 heads of state joined arms on Boulevard Voltaire, there was one notable absence.
At least, the absence was noted by many of Barack Obama's critics, who slammed the US president for failing to attend the French unity demonstrations following the attack on the satirical magazine Charlie Hebdo.
CNN's Jake Tapper said he was "ashamed" that Mr Obama, Vice-President Joe Biden or any other "high-level" US official failed to stand alongside leaders from the UK, Israel, the Palestinian authority, Germany and Jordan.
"I get that the president visited the French Embassy in Washington and that Secretary of State John Kerry spoke in French, and I certainly understand that the American commitment to security in Europe rivals no other," he writes. "But with all due respect, those are politicians spending money that they didn't earn and sending troops whom they don't know."
He also cites leading Republicans for failing to take the opportunity to visibly demonstrate their support and wonders why.
"I hope it's not American arrogance, a belief that everyone should express shock when something bad happens to us but that our presence at an international rally is worth less than a ticket to the Green Bay game when the victims speak in accents we don't understand," he writes.
In a Monday afternoon press conference, White House spokesperson Josh Earnest said Mr Obama wished he could have attended, but the "onerous and significant" security preparations for a presidential visit require more than the 36-hour advance notice the White House received.
He added, however: "It's fair to say that we should have sent someone with a higher profile."
Mr Kerry, who is in India to meet with Prime Minister Narendra Modi, said: "The US has been deeply engaged with the people of France since this incident occurred", adding that he will travel to Paris later this week.
Politico's Edward-Isaac Devore isn't so sure about the security excuse, however.
"As a general rule, the Secret Service doesn't let either Obama or Biden be in the open air in areas that haven't had a full security sweep, and the White House tends to be mindful of having security precautions create distractions around events," he writes. "But a forceful president could dismiss such concerns to make a public point about terrorism."
Besides, tweets Borzou Daragahi of the Financial Times, the world politicians didn't really lead the marchers through difficult-to-protect portions of Paris so much as join arms in a "photo op on an empty, guarded street".
According to Gateway Pundit's Jim Hoft, it's all just a question of priorities.
"The Obama administration sent three representatives to Michael Brown's funeral in Ferguson, Missouri," he writes. "But only the ambassador to France made the historic anti-terror march in Paris today."
The New York Daily News editorialised against the president, printing "You let the world down" on the front page of its Monday edition.
"This was a day to show up and to stand up, for the kind of march about freedom and courage and principles that this country has always done better than anyone," Daily News columnist Mike Lupica writes. "This is what the best and most noble of our marches on Washington must have looked like to the rest of the world."
Lupico concludes by pointing out that the US has a "complicated" relationship with France.
"Certainly there have been times when the leaders of France could have done better by us," he writes. "We should have done better by them on Sunday."
It was likely an oblique reference to the animosity that boiled over in US politics and the press as a result of French intransigence in the run-up to Iraq War in 2003. Many of the same conservative critics who today are blasting Mr Obama for failing to express solidarity with the French were cracking jokes about French cowardice and replacing "French" with "freedom" on congressional cafeteria items.
Twelve years is an eternity in politics, of course, and now the Obama administration is left facing a chorus of criticism - and not just from the usual voice on the right.
"I have been a fairly consistent supporter of President Obama's policies," writes Rick Ungar for Forbes. "However, President Obama's unwillingness to attend the Paris march is a personal failing on his part that I believe does damage to the pride and soul of the nation he leads."
As Jeffrey Goldberg of the Atlantic tweet: "It would have been nice to see the country whose birth was midwifed by France send its leader to stand with France today."
While the White House's intentions may be good, writes Bloomberg's Josh Rogin, it's just another example of how this administration can be tone deaf when it comes to "doing the small things that can make a big difference when it comes to maintaining relationships and showing respect".
"The White House often misses opportunities and lets poor optics overshadow positive contributions," he concludes.
Avoiding those kinds of unforced errors is pretty much what diplomacy is all about.