Washington (AFP) – Joe Biden faces the prospect of a crippling strike by railroad unions that could stall transport of fuel, corn and drinking water, dramatically complicate holiday season train travel, and dent the US president’s political standing. If an agreement is not reached by December 9 at the latest, the world’s largest economy could see nearly 7,000 freight trains grind to a halt, at a cost of more than $2 billion a day, according to the American Association of Railroads. Biden himself has got “involved directly” in the negotiations aimed at averting a work stoppage, White House spok…