Go where the beef is
Of course the real dealings with Latin America have to occur in the real areas you mention such as energy, trade and of course migration, and there, if the US was to find a more constructive approach to Latin America, it needs primarily to start looking for a more constructive and consistent approach among themselves, in Washington at least.
The Inter-American Development Bank recently reported that the working migrants of Latin America remitted to their home countries $62.3bn in 2004 and if these represented 15% of what the workers earned, we are then talking about a yearly figure of around $415bn, of which the US contributes almost all, and clearly this beats anything that what Castro and chávez can come up using the money obtained by selling Venezuelan oil.