When the United States said last year it would host the 2022 Summit of the Americas, officials had high hopes the event would help repair Trump-era damage to relations and reassert U.S. primacy over China's growing clout in Latin America. But on the cusp of the coming week's gathering in Los Angeles, U.S. President Joe Biden faces a struggle to make a success of a summit plagued by problems before it even began. Ideological discord over who to invite, skepticism about U.S. commitment to Latin America, and low expectations for major accords on issues such as migration and economic cooperation...