ROUYN-NORANDA, Quebec—One of the world’s largest miners is digging into America’s junk drawers, old phones and landfills. The quarry: bits of copper to meet the needs of the energy transition and data boom. Shredded cellphones, obsolete computer cables and chewed-up cars are heaped 30 feet high outside Glencore 97-year-old copper smelter deep in Canada’s sparsely populated boreal forest.