How does Houston, Texas, a massive city, deal with the pressures of immigration, an exploding youth population and a widening divide between rich and poor? The answer could be critical to the future success of the USA. Sociologists who have studied the city for decades believe that many US metropolitan areas could look like Houston in 30 years' time. Since the election of Donald Trump, these issues have become even more critical.Catherine Carr travels to the Texas to see how the city’s authorities and inhabitants are coping with the radical changes to Houston’s demographics and meets the pioneers attempting to intentionally build bridges across city divides.Picture: Houston's buildings, Credit: Getty Images