"Several nations begin warring with one another for the last stores of fossil fuels, namely oil and uranium. Known as the Resource Wars, fighting begins in April of 2052 and continues until October 23rd, 2077. China invades Alaska in the winter of 2066, causing the United States to go to war with China and using Canadian resources to supply their war efforts, despite Canadian complaints. Eventually the US annexes Canada in February of 2076 and reclaims Alaska eleven months later. After years of conflict, on October 23rd, 2077, a global nuclear attack occurs. Nobody knows who strikes first, but in less than two hours most major cities are destroyed. The effects of the attack will not fade for the next 100 years. As a consequence, humanity lives in underground Vaults though some people affected by the radiation live topside."

I'd say we're headed this direction.