REalloys (NASDAQ: ALOY) and a small number of other North American companies are doing what the rest of the Western world failed to do for three decades: They are breaking China’s "kill switch" on the U.S. defense supply chain. While the U.S. defense sector has long been reliant on international processing for these materials, REalloys has established itself as the only North American facility currently producing the specialized alloys essential for high-performance magnets used in advanced defense systems.China’s dominance isn't in…