The Earth is a sphere1 and every point on its surface has a point on the surface on the exact opposite side. The name for two such points are antipodes. (Singular: antipode.)
In American popular culture, China is the country you’d reach if you could drill all the way through, but that’s not quite right. China has about the right longitude to be on the other side, but not the right latitude. If you drilled a hole through the exact center of the Earth from the United States, you’d hit water.
In fact, you’d hit water if you drilled straight down almost anywhere on land. As an oddity of Earth, almost no areas have land-to-land antipodes. The most significant exceptions are eastern China and Southeast Asia (paired with South America, not the United States) and Antarctica (paired with parts of Canada, Greenland, Russia and a tiny bit of Alaska).
If you and a friend have access to a pair of antipodes, you can lay pieces of bread on the ground an make an Earth Sandwich. There is definitely nothing better you could be doing with your time.