From what I understand of the case, the cash was smuggled from the US to Mexico and deposited into accounts with HSBC based in Mexico. Consumer goods were then purchased in Mexico and shipped to Colombia and elsewhere (but not the US). While there should have been a lot more local oversight for money laundering, why should US government agencies have access to bank accounts in Mexico to determine if there has been money laundering activities?

This is a local matter, as it is in other jurisdictions, and the US can formally complain through the established channels, treaties, and agencies which allow for sanctions to be placed on banks and jurisdictions where there is excessive money laundering activities and low oversight.