Final answer:
Congress not having the power to control interstate commerce had a negative effect on trade relations, allowing for unfair practices and hindrances to domestic trade.
Step-by-step explanation:
The power of Congress to control interstate commerce has had a significant impact on trade relations between states. Prior to Congress having this power, states would often discriminate against each other, creating unfair trade practices. Without the ability to regulate trade, the government could not prevent foreign countries from flooding the market with inexpensive products, hurting American competitors. Additionally, states could pass laws that interfered with domestic trade, further exacerbating economic challenges.