The issuance of the Proclamation of 1763 did more than almost anything else in this period to unite the colonies and push them to discover their mutual interests.  Up until now, some of the largest colonies--New York, Pennsylvania, Virginia--had been squabbling over competing land claims on the Ohio country.  Vague colonial charters failed to draw an effective western boundary, and all had ambitions to claim the rich land.  During the Albany Congress, when Benjamin Franklin had proposed a united colonial effort for defense, the colonies had been unable to come together for fear of losing a future advantage on the issue of land claims.  In one fell swoop, the Proclamation of 1763 removed that bone of contention, while simultaneously giving all these colonies a common grievance.  Now they could turn their attention from the west to their own situation in the east, and to what Britain was "up to" there.  [I like to use the analogy of a children's playground to describe this situation.  Let's say you have a dozen children at play, and only one toy.  All will be fighting and competing for the one toy.  Now, let's say you, the adult, step in and take away the toy.  No more fighting, yes, but will you have peace?  No way!  Because now you have a dozen children angry at you for taking away their toy!  This is more or less what happened to the "mother country" with respect to the Proclamation of 1763.]