After the 1998 embassy bombings, the U.S. government tried to develop a clearer picture of  Bin Laden's finances. A U.S. interagency group traveled to Saudi Arabia twice, in 1999 and 2000, to get information from the Saudis about their understanding of those finances. The group eventually concluded that the oft-repeated assertion that  Bin Laden was funding al Qaeda from his personal fortune was in fact not true. The officials developed a new theory: al Qaeda was getting its money elsewhere, and the United States needed to focus on other sources of funding, such as charities, wealthy donors, and financial facilitators. Ultimately, although the intelligence community devoted more resources to the issue and produced somewhat more intelligence, it remained difficult to distinguish al Qaeda's financial transactions among the vast sums moving in the international financial system. The CIA was not able to find or disrupt al Qaeda's money flows. The NSC staff thought that one possible solution to these weaknesses in the intelligence community was to create an all-source terrorist-financing intelligence analysis center. Clarke pushed for the funding of such a center at Treasury, but neither Treasury nor the CIA was willing to commit the resources. Within the United States, various FBI field offices gathered intelligence on organizations suspected of raising funds for al Qaeda or other terrorist groups. By 9/11, FBI agents understood that there were extremist organizations operating within the United States supporting a global jihadist movement and with substantial connections to al Qaeda. The FBI operated a web of informants, conducted electronic surveillance, and had opened significant investigations in a number of field offices, including New York, Chicago, Detroit, San Diego, and Minneapolis. On a national level, however, the FBI never used the information to gain a systematic or strategic understanding of the nature and extent of al Qaeda fundraising. Treasury regulators, as well as U.S. financial institutions, were generally focused on finding and deterring or disrupting the vast flows of U.S. currency generated by drug trafficking and high-level international fraud. Large-scale scandals, such as the use of the Bank of New York by Russian money launderers to move millions of dollars out of Russia, captured the attention of the Department of the Treasury and of Congress. Before 9/11, Treasury did not consider terrorist financing important enough to mention in its national strategy for money laundering. 
What kept the U.S. government from being able to stop  Bin Laden's flow of money?
Needed to develop a clearer picture of  Bin Laden's finances, but were unable to determine where the source of the money was coming from. Ultimately, although the intelligence community devoted more resources to the issue and produced somewhat more intelligence, it remained difficult to distinguish al Qaeda's financial transactions among the vast sums moving in the international financial system