"He must be meaning colonial-era America."
A threat to the world?
Does he mean a threat to existing world order at the time? In general, the European powers' drive to incorporate new lands for new products and commerce heightened their tensions and it ended up in the Seven Years War in the mid 18th century (the French and Indian War was in fact the North American thretre of that particular war). So in a sense the existence of America drove the Western European nations more antagonistic.