It means from coast to coast, across the entire country.
Their plan was called the Anaconda plan.
They wanted to blockade the Southern coast to prevent them from receiving resources from other countries. They also wanted to capture the Mississippi River to effectively cut the Confederacy in half (Battle of Vicksburg). The final step in their plan was to capture the Confederate capital city (Richmond).
China demonstrated its willingness to open talks with the United States by "<span>B. opening trade with American companies," since this was believed to be in the best interests of both China and the US. </span>
