While I agree with aboutillegals that Spanish colonialism were not an amorphous blob, there was a major difference between the sense of identity that colonists in British North America developed and, as far as I can tell, that in Spanish America. Probably the most important contributing factor to this was that Spanish colonies were mostly royal colonies - meaning that they tended to be settled at the Spanish crown's behest, and quickly settled into the Spanish system of political organization. Conversely, British colonialism was significantly less centralized. Some colonies began on the basis of religious asylum. Others were proprietorships. Others began as business ventures.

Broadly speaking, though the British system was more inclined towards commerce, whereas the Spanish were more interested in resource extraction. This meant that Britain had less incentive to exercise tight control over its colonies, because they would continue to sell their goods and buy British goods whether the British authorities were breathing down their necks or not. Spain, on the other hand, could not necessarily reap the same rewards if they adopted a laissez-faire model of colonialism. Much of their early colonial ambitions were based on extracting precious metals, which required supervision, and thus a top-down governmental structure. British decentralized benign neglect was one factor that allowed them to develop distinctive cultures.

The most important recent book that compares British and Spanish colonialism is J.H. Elliot's Empires of the Atlantic World (2006). It's not a perfect book, but has lots of good information on the differing governmental structures at play.

Mainly due to religious splits and factions. North America was so big and "unclaimed" that different groups got different charters for separate areas. They expanded, and in some cases splintered, but since their right to govern came from a number of different charters with the British Crown, and they all didn't get along perfectly they never merged together.

Well the British learned a few tricks, and the American Revolution was sort of a perfect storm of stupidity. The revolution was more of a response to a number of British over responses to smugglers- such as the Boston tea party which was made of smugglers upset that their profits were getting cut into by the British repeal of some unpopular taxes - and other factions that unintentionally pissed off everyone else. Edit: Coupled of course with a rather tumultuous time in British Politics and international relations.

Weren't the French/Spanish/Portuguese's American holdings large centralized, amorphous blobs?

I can speak for the spanish holdings. They were not centralized, it was broken up into viceroyalties and audiencias. These entities were in direct connection with spain, and didn´t had too much of contact or trade between themselves.

Each of these entities had their own economy, political elite and judicial system (own in the sense of independent from each other, but not from spain). They weren´t really interested in each other, but in their relationship with the imperial center. These entities became later on the basis for latin american countries.

At the time of the Revolution, there were 21 British colonies in North America. The 13 that became the original United States, plus Canada (Quebec), Nova Scotia (Nova Scotia and New Brunswick), Prince Edward Island, Newfoundland (Newfoundland and Labrador), East Florida, West Florida, Bermuda, and the Bahamas. (Maybe also Turks and Caicos).

13 became part of the United States. East and West Florida were taken by the Spanish. The rest remained British North America.

The many different colonies in British North America came about because they were founded by different groups under different charters (Virginia, Plymouth Plantation, Massachusetts Bay Colony, North and South Carolina, Maryland, New Hampshire, Connecticut, Rhode Island, Pennsylvania, Newfoundland, Bermuda, Bahamas) or founded as colonies by other European Nations and captured by the British (New York, New Jersey, Delaware, Canada, Nova Scotia, Prince Edward Island, East Florida, West Florida)

The French colonies were not amorphous blobs. Acadia (Nova Scotia and Prince Edward Island), and Canada were two separate French colonies. The Floridas were separate Spanish colonies from Cuba, Santo Domingo, Puerto Rico, Mexico, etc., so the Spanish colonies were also not amorphous blobs.

How come nothing like the American Revolution happened in Canada, Australia or New Zealand?

It didn't need to happen here in Australia. In short, the local Australians said "Hey, cobbers, we'd like to be an independent country because we don't think you Brits have our best interests at heart out here in Asia and the Pacific. Don't worry, mates, we're still good British blokes and loyal members of this bloody great British Empire, but we want our own local true-blue dinky-di government in this great southern land of ours." and the Brits said "Sure thing, chaps! Send us the paperwork and we'll get it passed by the Parliament and get the jolly old Queen to sign it for you. Pip, pip, tally-ho, and all that."

I've written more about this subject here and here.

This is a good and complex question, so the answer will come in several parts.

First and foremost, remember that Britain's expansion into North America were not a centrally-planned, government-directed affairs made by officials looking at a complete map. Colonization was a chaotic, haphazard process, driven as much by ambitious (and frequently violent) frontier adventurers as by any kind royal decree.

The first two permenant British colonies, Jamestown (1607) and Plymouth (1620) were private ventures corporate ventures. So was the later colony of Georgia. This was itself a mark of the relative economic freedom enjoyed by the British compared to the more tightly organized kingdoms of France or Spain. These colonies usually had pretty rough borders, including some that granted "sea to sea" ownership - up until after the Revolution, some of the New England colonies claimed that their borders ran around (or through) New York and extended out to the Pacific. This nearly led to a shooting war between Pennsylvania and Connecticut on a few occasions, not to mention long-simmering hostilities between New York and New England that still shaped politics during the American Revolution.

Now, I mentioned a New York there, and used the phrase New England. New York was originally a Dutch colony conquered by the English. As such, it remained largely culturally and ethnically distinct from the other British colonies throughout the colonial period.

The phrase "New England" is the survivor the an attempt by the Charles the second to try to centralize control of North America through the creation of proprietary colonies, given personally to loyal supports . The Dominion of New England, a conglomaration of the various colonies that had grown out of Plymouth and Massachusetts Bay, was given to Edmond Adros, Dutch New Netherland to the Duke of York, and a great, wooded rectangle to William Penn. New England eventually broke apart after the Glorious Revolution, but New York and Pennsylvania survived intact.

For more, see The Peopling of British North America by Bernard Bailyn.

The American Revolution is sometimes referred to as the ending of the first 'British Empire'. By the time the rest of what is now the Commonwealth was being colonised, the British diplomats and settlers had really learnt their lesson from America and worked in a bit more with their men on the ground, and in the cases of India and New Zealand at least, with indigenous rulers and chiefs. Empirical politics was far less reactionary post-revolution, possibly to do with the ending of the idea of absolute rule of the monarch by the early 19th C. Anyway, so far as I know this would be the main reason, they simply became better empire builders, with a more flexible and efficient bureaucracy to run the colonies.