Simplify the following text for a Grade 11 native English-speaking person.
Original: This act was of immense importance in the subsequent history of Western and Central Europe in general , for Clovis expanded his dominion over almost all of the old Roman province of Gaul ( roughly modern France ) .
Simplified: This act was very important in the following history of France and Western Europe in general , because he expanded his reign over almost all of the old Roman province of Gaul ( roughly modern France ) .