How might the Americas have been different if the Spanish had not colonized there?

There are a couple of differences:

1) The Americas (especially Latin America), will not have Roman Catholic influences in the area, and will not have it as their state religion.

2) The land will keep most of it's natural wealth, though it may not be used in great quantities as before.

3) Population will not take a hit, and will continue to grow, as European diseases are not spread to them. However, if trading occurs between the north-eastern tribes all the way down to Central America, they will still be exposed to diseases carried by the French and British.

4) They may not be exposed to the usage of firearms as quickly, which may lead to their demise to their native enemies. Firearms, while they took very long to reload back then, was a symbol of power and was used more as a shock then as a weapon (until the mini-ball, repeater, and other upgrades to the rifle came).

5) The other way to look at it is that another European Power may take over those lands. The first of which is Portugal, whose lands were very near the Spanish territory. The next in line would be France, which borders the Spanish territories, and than Britain.

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what was the significance of the plessy vs ferguson ruling and jim crow laws

answer the impact. plessy v. ferguson allowed 'separate but equal, also known as segregation, to become law in the united states