Mercantilist policy. Make colony, sell raw resources homeward, make goods, sell back to colony and non-colonial markets. Keeps the coloniser rich. Without a need to expend on infrastructure when you only need mines or plantations etc. colonies were left as just that. Add tropical weather, soils and diseases etc (where in the tropics obviously) and stuff isn't easy. Great for tourism, less so for certain crops and certainly not great weather for seriously competitive industrial machinery with the increased rust/corrosion.

It's wrong to use the term 'first world' when describing the powers that settled in the Americas. Settling a colony was not meant to make those who colonized better, despite the propaganda of the white man's burden. The point was to profit. The wars that were fought for independence did not always leave the best person in power, often times they would just line their own pockets.

This is a question that is VERY tough to answer. semaj009 has more or less answered it. J.H. Elliott's book, "Empires of the Atlantic World: Britain and Spain in America 1492-1830" sought to answer this question precisely, though his conclusion is certainly not agreed by all historians. My answer is largely based on his answer. As semaj009 has rightly pointed out, a mercantilist economy means that you are basically extracting resources from a colony and offering little in return. However, the key difference between British colonies and Spanish colonies was over precisely this arrangement. British colonies retained a much larger degree of independence from the crown and could also rely upon a much more steady supply of manufactured, industrial goods. Furthermore, and this is where Elliott's argument is harder to make, British colonies engaged in greater degrees of independent civic participation which planted the seeds of democratic development. Spain's industrial revolution was much slower and sporadic than Britain's and therefore Spain could provide very little in return to its colonies,even though it continued to extract the colonies' resources. Spain's domestic economy was so heavily regionalized that little of what occurred in Spain was felt in the colonies, and vice versa. Really, only the economies of Seville, and to a small extent, Catalonia, actually maintained solid economic connections with the colonies. Secondly, Spain's colonial apparatus was more centralized compared to Britain's decentralized model, which meant that once the Spanish colonial machinery of state was removed from Latin America, Latin American states had a much harder time building self-government. Since British colonies had lived more independently, it was easier for them to build an independent state. Again, I agree with Elliott's point about Spain's lack of industrial output... the harder argument to make is whether Latin America's stagnation and the United States' success can be drawn to a centralized vs. decentralized colonial model. We could point to a bunch of other ways in which Spanish colonies were more democratic than British ones and vice versa so I won't get into that debate. But I've articulated one position in this debate that makes sense to me.