That was one of Romney's vague, unsubstantiated hyperboles from today's policy-empty announcement. Politifact declares it's "so far off base that it's ridiculous." According to the Heritage Foundation's study on an index of economic freedom:
The U.S. ranked ninth out of 179 nations on the list, with a score that placed it near the top of the "mostly free" category. The only nations to be considered more "free" than the U.S. were, in descending order, Hong Kong, Singapore, Australia, New Zealand, Switzerland, Canada, Ireland, and Denmark.
What's maddening is the use of the short-term impact of a recession on revenues and equate it with a permanent shift in American governance. But context must matter. If Obama had come in with a boom at his back and had then raised government spending as a percentage of GDP from the lower 30s to the upper 30s, Romney would have a point. But he doesn't. The president who grew government during years of economic growth was George W. Bush.
Or maybe Romney's assertion was not intended as a factual statement.