As the United States of America celebrates the 250th anniversary of its independence, it is useful to reflect on the nation's ascent. A virgin territory for European colonisers provided a fresh start escaping the encumbrances, distinctions, hatreds and internecine wars of the Old World. Forests have been overharvested.The US's oil reserves may last for roughly 50 years, depending on consumption and new discoveries. Tesla views itself as a technology firm, recycling a product first considered by Thomas Edison and Henry Ford. This immigration phobia is counterproductive given American dependence on foreign skills and cheap labour.