The British were in the renouncing of their citizenship. In this almost feeble act they, captured navy vessels and impressed them to fight for them also by taking or destroying the ships.
The British were driven during the Napoleonic wars in which was between Britian and France. The neutral land of U.S.A was unnecessary but somehow without their consent dragged into the fight.
The impressement was very important at the last because it drove the war between Britian and America faster. It also paved the path to the Embargo act. (Which was eventually taken away due to the economic monstrosities.) It also added to the royal navy.