On Sunday, Feb. 26, the sermon at the Spanish-language Mass in Waterloo, Iowa, was about fear. Like many Catholic churches, the tan-brick, gothicQueen of Peace serves as a community center for Hispanic immigrants in this Cedar River town of 68,000. Waterloo has a claim to be Iowa’s most diverse big city. Immigrants, including Latinos and refugees from Bosnia, Myanmar, and Liberia,have helped stabilize its population andhousing market, and revived downtown storefronts.