Napoleon's Continental System intended to blockade the UK from trade from the rest of the world, so that loss of food and raw materials would cripple the UK economy which was financing the wars against him. The Orders in Council were intended to counteract this. Of course the French did not have the naval resources to enforce this. The UK did.

The American merchant marine quadrupled in size during this period. And they were keen to get experienced seamen from wherever they could. British seamen had a duty to serve in the Navy when called upon, a duty that had existed since Tudor times. You couldn't change this by suddenly becoming American.

I'm not saying that any of this was right and fair. I'm just saying that it happened.