The president of the Democratic Republic of Congo (DRC), Félix Tshisekedi, has reached out directly to President Donald J. Trump with a historic proposal: help defeat a brutal rebel force terrorizing his nation, and in return, America will gain direct access to one of the world’s richest untapped troves of critical minerals—worth an estimated $24 trillion. According to a letter obtained by The Wall Street Journal, President Tshisekedi offered Trump exclusive mining opportunities through the newly launched U.S. Sovereign Wealth Fund, a Trump-led initiative aimed at reshaping global investment through pro-American partnerships. “Your election has ushered in the golden age...