Complex sentence: The second charter also tried to cut off all contact with foreigners, especially the competitive Americans, but this strategy backfired since the Russian colony had become used to relying on American supply ships, and America had become a valued customer for furs.
Split into simpler sentences: The second charter also tried to cut off all contact with foreigners, especially the competitive Americans. This strategy backfired since the Russian colony had become used to relying on American supply ships, and the United States had become a valued customer for furs.