What were the strengths and weaknesses of the New World?

Mesoamerica was as "civilized" as most of the rest of the world. They did not have a metallurgical technology, but the weapons they had were quite sophisticated, and the Aztecs gave Cortés and his army quite a fight before scumbling to disease. The main weakness was their vulnerability to Western diseases, which wiped out more than half the Native American population, and by some estimates maybe as much as 98% before the European expansion ever got under way.

Old:

It was already civilized

It had strong governments

Trade links to other countries

Good economies

The cities were overcrowded

Disease ran rampant

New:

Rich in important Natural resources

Vast amount of land available

Lacking in new technology

Lack of population encouraged slavery

The New World in the 15th century did not "lack civilization," you racist idiot. It had many highly-developed civilizations and had had them for centuries.