The French and Indian War (1754-1763) should be thought of as part of a worldwide struggle between the British and French. That conflict is better known as the Seven Years War.
The main cause of the French and Indian War is the superpower competition between Britain and France. These two countries were the most powerful in the world and competed for dominance around the globe.
Within this overall cause, there were reasons specific to North America that helped cause the war.
1. The desire on the part of both countries to control the lucrative North American fur trade.
2. The fact that the expansion of the British colonies in North America were threatening French territory and their trade routes.
These three factors (which can be seen as two subfactors of a main cause) were instrumental in causing the French and Indian War.
The French and Indian War was fought between the two greatest powers on earth. The British and French had been rivals for a very long time in Europe. By 1754, the rivalry had followed them to North America.
The French had long enjoyed a very profitable business with the fur trade. The French had settled in the Ohio River valley, while the British were on the Atlantic coast. British colonists had moved into the Ohio River valley by 1754 and began competing with the French in the fur trade.
Not only were the French and British competing for dominance in Europe and in North America, they were also competing for trade in other parts of the world like Asia.
These are the causes of the French and Indian War.
They wanted to monopolize the fur trade in North America and the French felt the British were threatening their territory as the British expanded. They were fighting in terms of trade and dominance of the region.