South Korea has more reason to fear invasion of enemy tanks than almost any other country in the world. The DMZ has been armed to the teeth since a cease fire was reached in the Korean War, half a century ago (there is no true peace treaty), and no country in the world devotes a larger share of its resources to national defense than North Korea. South Korea's capital city is Seoul is also less than an hour's drive from the border.
Not surprisingly, Soth Korea has, as a result, invested considerable effort into designing a next generation tank of its own. The result, the KNMBT will weigh in at 55 tons. The main battle tank used by American forces, the M1, weighs in at 70 tons, about 27% larger. This extreme weight has made it difficult to get M1 tanks to the field, as only the largest airlift planes (the C-5 and C-17) can carry them and even then only one at a time (stripped down in the case of the C-17), they are too big to pass through some narrow urban streetscapes, and they are often so heavy that civilian road and rail bridges cannot support them.
When a country far more likely to see tank to tank combat than the United States produces a far lighter tank, that is a pretty good indication that the American version is overweight.