Barack Obama's visit to Chile, Brazil and El Salvador next week should not awaken hopes of enormous results. The United States has had little to do with the best things that have been happening there: the explosion of the middle class and the marginalization of the extreme left. The negative events, on the other hand – the violence deriving from the war on drugs – has much to do with United States policies, which will take years to change.

Latin America and the Caribbean lack a great deal: only Chile and Barbados are ranked among the 50 most competitive economies. Their universities produce six social scientists for every two engineers. And the flood of money seen coming into these countries is due, in part, to the Chinese demand for their "commodities." But there have been notable strides forward thanks to investments and commerce. The poverty rate has fallen to a third of the population – 30 million Brazilians have been added to the ranks of the middle class in eight years – and Peru, Colombia and Panama are experiencing a bonanza, while Chile is back in good shape since its earthquake last year.

The last time the United States suggested a common vision for the region was with the Free Trade Agreement of the Americas. Once that proposal failed, Washington lost interest. In a certain sense, the economic take-off has happened in spite of some North American policies: six Brazilian export products lack protectionist barriers in this market, and the United States Congress never ratified the Free Trade Agreement Colombia signed five years ago. The progress is due above all to a broad political consensus in favor of the democracies of the market. As the reformed Salvadoran ex-guerrilla Joaquín Villalobos said: "Natural resources, foreign aid, free trade agreements and loans do not have as much of an effect as political maturity."

One consequence of this consensus has been the decreasing influence of the antediluvian left, that is to say Cuba and Venezuela, supported by Bolivia, Ecuador and Nicaragua. One of Obama's hosts, Mauricio Funes, has frustrated the efforts of his party, the Farabundo Martí National Liberation Front, to align El Salvador with Venezuela, while Uruguayan President José Mujica, once a terrifying guerrilla fighter, is now a boring Social Democrat. Even the Paraguayan Fernando Lugo, who once knocked on the doors of revolutionary chaos, has been seducing foreign capital.

Hugo Chávez suffers from the chronic debacle which he incubated. His main South American ally, Bolivian president Evo Morales, is now loathed by two thirds of his country. Nicaraguan Daniel Ortega is trying to get himself re-elected in spite of a constitutional prohibition, but this is due in part to the gift of a divided opposition.

In this case too we can say that the constriction of the lunatic left – an even more transcendental event than the economic boom – owes little to United States influences.

The other side of the coin is the nightmare of public disorder fed by the war on drugs. Here indeed United States policies are a factor. During the 90s, under pressure from Washington, coca cultivation jumped from Peru and Bolivia to Colombia. When Colombia tightened the screws, it jumped back over to Peru, where the area devoted to coca cultivation has increased by 70 percent, and production has tripled. The same game of musical chairs has been played out along the drug supply routes. When the U.S. closed the Caribbean corridor, Mexico took over.

In spite of the fact that several North American states allow medical use of marijuana, and that personal use is no longer the object of intense persecution in the United States, Washington's anti-drug policies vis-à-vis Latin America have not changed one iota.

The result is an inferno in countries where there is an endless influx of weapons from the United States (Mexico has confiscated more than 100,000 automatic weapons that entered the country from north of the border.)

Obama knows all this, but he hasn't got the stomach, at the moment, for the prolonged fight that it would take to make a change in anti-drug policies. And until that happens, as I recently had occasion to hear Mexican President Felipe Calderón say, it is not realistic to expect that some Latin American country will defy Washington on its own.