Well, it's not in the United States. The information is transmitted to the United States, and then the driver arrives at the customs inspection booth. The U.S. has that data in advance. The e-manifest allows the U.S. to have that information before the driver arrives. It allows them to risk-assess the data with respect to the driver and the cargo and decide whether they have an interest in the individual or the cargo he's carrying.
On May 1st, 2007. See this statement in context.