Baloney. America's most successful and famous entrepreneurs almost ALL started after they were middle-aged failuers: Ray Kroc didn't come across McDonald's until he was in his late 40s selling Dixie Cups; C. W. Post was a failure at everything and in a health asylum, broke, when he invented Postum and Grape Nuts; Mary Kay Ash had two kids and no husband when she started her own cosmetics company at age 50; P. T. Barnum didn't create his famous circus until age 70!!!; the guys who invented Home Depot were both in middle age and not particularly successful as I recall.
This is an EXCUSE! But age never stopped any strong-willed entrepreneur from getting a job or starting a business.
Please cite such a story from an era in which the USA was not employing protective tariffs. further Phineas T Barnum was a sucessful showman long before he created his circus.