Remote patrol

"The American Experience" begins another season as TV's liveliest historical documentary series at 7 tonight on Channel 19. Tonight's three-hour special, "America 1900," depicts a United States full of vigor and optimism. The country has asserted itself as a world power in breathtakingly short order. But as narrator David McCullough reminds us more than once, there is a price to pay for that exuberance: environmentally, politically and socially, America is losing its innocence fast. Also tonight, "Hey Arnold! " observes Thanksgiving a week early (7 p.m. on Nickelodeon), and "Garth Brooks Live" features the country star in real time at 7 on Channel 41.