AVONDALE, Pa. — In this sleepy, rural corner of southeastern Pennsylvania that produces 70% of the nation’s mushrooms, President Donald Trump’s immigration policies are threatening the American dream for a tight-knit community of generational mushroom farmers and the immigrant workers they have long employed. The year-round work of growing and picking the mushrooms that season the stews and stir-fries on American tables is the basis of the local economy in Avondale, a town of just over 1,200 people where more than 60% are Latino. In recent weeks, several immigrants in the area have already been arrested by federal immigration officials...