Final answer:
A decrease in foreign demand and a relative price increase of U.S. goods would have a negative effect on the United States' aggregate demand.
Step-by-step explanation:
A decrease in foreign demand and a relative price increase of U.S. goods would have a negative effect on the United States' aggregate demand. When foreign demand decreases, there is a decrease in exports, which leads to a decrease in aggregate demand. Additionally, when the relative price of U.S. goods increases, it makes U.S. goods more expensive compared to foreign goods, leading to a decrease in aggregate demand.