What effect did the introduction of smallpox have in the americas

It contributed to the defeat of American Indians, is the right answer.

Explanation:

The Columbian Exchange has remained one of the most significant event in the history of the United States and Europe. This exchange not only changed ideas, beliefs, goods and services but also diseases. As soon as the settlers began to conquer the territories of the native population, they came into their direct contact. The smallpox was a crucial factor that led the Europeans to easily conquer their land. For instance, the smallpox devastated a large number of American Indian population that directly resulted in a reduction for the troops to fight against the new settlers.

the constitution gives congress the power to regulate commerce "among" the several states.