Obama Becomes First U.S. President to Address African Union

ADDIS ABABA, Ethiopia—President Barack Obama on Tuesday became the first American president to address the African Union in the institution’s 52-year history, a moment lauded for its historical significance but one that underscored how far behind the U.S. is in investing in the continent.

Mr. Obama’s visit capped a five-day African trip where he pledged enhanced U.S. economic ties. The U.S., however, is playing catch-up to other...