And it will continue to be spent, because that amount is dwarfed into insignificance by the value of trade that passes through the ports of New Orleans and Baton Rouge, as well as the industries that line the banks of the Mississippi.
There is some justification for federal money to be spent on the Mississippi River and the gulf ports, as interstate/international commerce routes. Not to say that the specifics of how it’s been spent have been wise, but there is no constitutional reason why it’s not appropriate to direct federal funds to facilitate this interstate commerce route in accordance with the wishes of the many states which benefit from it. Funneling federal tax dollars to enable the construction and maintenance of homes and businesses in the New Orleans area (or any other area) is not justifiable under any reasonable reading of the Constitution.