Members of the proofreading public recently made the discovery and it went viral on microblogging site Twitter late on Tuesday, with people mockingly tweeting photos showing the "Amercia" message.
"Some poor app designer is getting strapped in a cage on the top of a car and driven across country tonight. #amercia," one user tweeted, in a reference to Romney's hard-to-live-down decision years ago to strap the family dog in its carrier on the roof of the car during a vacation.
On Wednesday, the app, promoted by official campaign website mittromney.com, had yet to be corrected, and new downloads contained the spelling error.
"Mistakes happen," Romney campaign spokeswoman Andrea Saul said on MSNBC.
"I don't think any voter cares about a typo at the end of the day," she said, adding that an update had been sent to Apple and was awaiting final approval -- and presumably one last spellcheck.