Final answer:
The U.S. receives the least direct solar energy during winter due to the 23.5° tilt of Earth's axis, which causes lower solar angles and shorter daylight hours, spreading the Sun's rays over a larger area. This results in less intense solar heating compared to when the Northern Hemisphere is tilted towards the Sun during summer.
Step-by-step explanation:
The reason the U.S. receives the least direct solar energy during winter, as compared to the rest of the year, is not due to the Earth's distance from the Sun. While it's true that Earth's orbit is slightly elongated, and the Earth is actually closest to the Sun in January, the amount of solar energy reaching the U.S. in winter is not governed by this factor. The key reason for less direct solar energy is the tilt of Earth's axis, which is about 23.5°. During winter in the Northern Hemisphere, the Earth's axis points away from the Sun, leading to lower solar angles and shorter daylight hours, causing the Sun's rays to spread out over a larger area and become less intense.
In contrast, during the summer, the Northern Hemisphere is tilted towards the Sun, resulting in more direct sunlight and longer days. This direct sunlight and the longer duration of daylight combine to warm the Earth effectively. Hence, the angle at which the Sun's rays hit the Earth, and the length of the daylight, are more crucial factors in determining the intensity of the seasons than the distance from the Sun.