Please give an example of a document that reveals greater US involvement than was known previously.

The documents I've seen revealed Ukrainian secrets. For example, they revealed Ukrainian casualty numbers and Ukrainian estimates of Russian casualty numbers.

Everyone paying attention before this leak knew that the US is giving significant support in the form of advice, money, and arms. Everyone knew that the US has a small number of military personnel in the embassy but isn't fighting in the war. Some people think this is bad, but it's not a secret.