Why did france declare war on spain and great britain as part of the french revolution?

Well France declared a treaty with the United States Colonies - this in turn began a world war. Spain allied itself with France and the war spread amongst the colonies of the world. The wars weren't fought on European soil but in the various colonies. The last shot of this conflict was actually in India. French involvement in the US Revolution actually sparked a "World War". Colonies in the West Indies, Africa and Asia were the prize. The only land or colony the English lost - was what became the United States. They defeated the French and Spanish in the West Indies and most importantly - India. India was the "crown jewel" of the English Empire.

After this world conflict, France was bankrupted and tired. Eventually it lead to the ousting of King Louis and the first of many French Revolution. Let me tell you, no country in the world benefit more from French misfortune then the United States. The US benefited from French involvement in it's Revolution - a war the French lost and left bankrupt AND when Napolean's France was desperate for cash, the US was able to buy the Louisiana Territories for pennies on the acre (we know it as Jefferson's Louisiana Purchase - which double, if not tripled, the size of the United States in land mass).