DARIEN GAP, Panama—The grind of heavy machinery breaks the silence of the Darién jungle, where the Pan American Highway ends at Yaviza in Panama. Construction workers have cleared towering trees to make way for a steel and concrete bridge mighty enough to withstand flooding from the Chucunaque River. An onsite worker for the construction company Cusa told The Epoch Times the construction project will cut 4 miles into the Darién jungle at a cost of $42 million and includes a second bridge crossing the Tuira River. That would leave some 55 miles to finish the Pan American Highway, also known...