"When our opponents say this nation is in decline they are dead wrong," he said. "This is America. We still have the best workers in the world and the best entrepreneurs in the world. We've got the best scientists and the best researchers. We've got the best colleges and the best universities."
He went on: "We are a young nation with the greatest diversity of talent and ingenuity from every corner of the globe so no matter what the naysayers may say for political reasons, no matter how dark they try to make everything look, there's not a country on Earth that wouldn't gladly trade places with the United States of America."
Days earlier, GOP vice presidential candidate Paul Ryan noted that the national debt was reported to have passed $16 trillion on the first day of the Democratic convention. "That's a country in decline," Ryan said.
Unemployment remains stubbornly high, clocking in at 8.1 percent on Friday and keeping joblessness and economic weakness on the boil as top campaign issues.
Obama opened a two-day bus tour in Florida, campaigning in a state with the highest elderly population and an unemployment rate of 8.8 percent, higher than the national average.
As both candidates enter the final two-month sprint to the election, Romney is casting Obama as an inept steward of the nation's post-recession recovery. It's a portrayal Obama has been fighting for months as the unemployment rate sticks stubbornly above 8 percent.
On Friday, the government reported that employers added just 96,000 jobs in August and that, aided by frustrated job hunters giving up, the jobless rate dropped only marginally from 8.3 percent the month before.