Lincoln extended the blockade to include Virginia and North Carolina because they had seized government arsenals, forts, and facilities. The first hostile actions came from them.
Because Lincoln applied the test of whether the United States courts and postal service were continuing to operate.
That was his pretext. He couldn't get a Southern governor to declare his State in insurrection, although he specifically invited at least one governor, Sam Houston, so to declare, by a secret letter. So Lincoln insurrected them himself by applying his little test. Which would have worked on any country in the world that was not, or was no longer, part of the American Union.