This is concerning Rotation. If it is dawn in the eastern United States, what is it in the western United States? Why? My answer --- It is nighttime. This is because the sun rises in the East and sets in the West. Is this correct?

That's right. I suggest you add that because the earth rotates toward the east the East Coast sees the sun about 3 hours before the West Coast.

http://www.physicalgeography.net/fundamentals/6h.html

it is day

Yes, your answer is correct. If it is dawn in the eastern United States, it would be nighttime in the western United States. This is due to the rotation of the Earth on its axis from west to east. As the Earth rotates, different parts of the planet are exposed to sunlight or darkness. When it is morning in the east, the western part of the United States is facing away from the Sun, causing nighttime. Therefore, the time difference between the eastern and western parts of the United States is responsible for the shift from dawn in the east to nighttime in the west.