How important is financial declaration to the US consulate while?
The declaration proves that you (or if applicable, your sponsor) have sufficient assets to live on while in the USA and thus are unlikely to become a burden to the USAs federal, state, and local governments. If you cannot satisfy the consular officer of this improbability, you will be denied a visa. Understand that if your country is not in the visa waiver list, the default position of the USA is that you are not acceptable for visiting, and you must convince the USA otherwise.