A Bank Tax will in no way support or sustain the economy. Such a tax would only reward the efforts of unscrupulous people who desire to spend money unwisely and then penalize American people by forcing them to pay for their financial excesses. This tax would be harmful to the people, and would benefit those who have already misused money poorly.
No, a bank tax will not help stabilize the economy, because banks are the driving force behind the economy. Taxing the banks will make all the banks lag. It is more important to allow banks to get back to lending. Taxing banks is just penalizing them for making a profit. It is a political move, and nothing else.