There is widespread animosity in Europe toward Johnson, who recently compared the EU's aims to those of Adolf Hitler.
Johnson was expected to stand for the Conservative party leadership in the wake of the referendum result, but did not put himself forward after key colleagues withdrew support.
Education Secretary Nicky Morgan, Culture Secretary John Whittingdale and Cabinet Office Minister Oliver Letwin were other aides of former prime minister David Cameron dropped from the frontline and pushed to the party's backbenches. "It's also bitter for the European Union", he added.
"She's got dyed blonde hair and pouty lips, and a steely blue stare, like a sadistic nurse in a mental hospital", he wrote of the Democratic candidate.
Upon hearing about Johnson's selection, State department spokesman Mark Toner told reporters that "the US will always work with the UK due to the "special relationship" between the two countries and that the US/UK relationship "goes beyond personalities". Johnson was considered an unlikely choice for the job and his preference elicited mixed reactions-ranging from bemusement to worry-from politicians and media outlets around the globe.
He also dismissed comments by French Foreign Minister Jean-Marc Ayrault that he had "lied a lot" during the Brexit campaign, saying he had just received a "charming letter" from his French counterpart.
Boris Johnson visits Bristol in November 2012 and heckles the hecklers
For the most part though, supporters of Johnson have been quiet online, possibly in fear of retaliation from singer Cher who reacted passionately to the news of his appointment. He has apologized before and seems likely to do so again he said after his surprise appointment that "the United States of America will be in the front of the queue" for the next Johnson apology, apparently because of his comments about President Obama's ancestry.
"(He has) his back against the wall to defend his country but also with his back against the wall the relationship with Europe should be clear", Ayrault said.
"And I think we now have the opportunity to achieve that", Johnson said.
The bookmaker has opened a betting market featuring May's first four new appointments, which includes Chancellor Philip Hammond, Home Secretary Amber Rudd, Brexit Secretary David Davis, and of course, Johnson as Foreign Secretary.
The French minister said he needs a negotiating partner who is "clear, credible and reliable" for the upcoming negotiations on Britain's stated desire to leave the EU.
"It is bitter for Great Britain".
In April, Johnson came under massive criticism when he recounted the story of a bust of former British Prime Minister Winston Churchill being removed from the White House to be sent to the British Embassy.