BEIJING — When the United States tightened up exchange strains with Beijing on Friday, the news was welcomed with exhaustion and premonition among the general population in China who will pay the prompt value: proprietors of production lines of all shapes and sizes. Rivulet Chen runs a plant in Shanghai that makes bags for brands including Samsonite. More than four-fifths of his requests originate from the United States. The exchange war, presently about a year old, has just pressed Mr. Chen's primary concern. American clients demanded that he bring down his costs so they wouldn't need to raise theirs. When he mulls over moving generation out of China — to Southeast Asia, for example — he stresses over losing access to China's tremendous production network and able work power. "This is absolutely an impasse," Mr. Chen said. "We lose benefits and need to close down. American merchants can't discover viable options that can convey items with a sim