Some counters, courtesy of Overcoming Bias:
The US had large and successful efforts, kept hidden for many decades, to move the fashion in art and writing away from Soviet styles, toward “modern” US styles.
… the US kept secret for 41 years that it faked its excuse for the Vietnam war, and for 46 years that it spied on citizen phone calls via Project Minaret. KFC has kept its recipe secret for 70 years, and Coca-Cola has kept its secret for 130 years. Venice kept its glass-blowing methods secret for many centuries, and China kept secret its methods of making both silk and porcelain for over a thousand years.