I have no real disagreement with you on any of your points about land reform here.  However, on this issue of US interests it is important to note the different geopolitical contexts between the 1970's when Allende was elected and the 2000's when the 21st Century Socialism wave occurred in Latin America.

In the 1970's the US was weaker politically, in still in a real contest for power over the world it conquered in WWII, due to certain rebellious Communist powers armed with nuclear weapons. A wave of anti-US, democratically elected governments throughout Latin America of the kind that occurred in the mid-2000's would have been very precarious for a US that was still struggling for supremacy with the USSR at the peak of its power.

By 2005, the US was supreme again in the world by any objective measure, with its own military expenditures being more at the time then those of the entire rest of the world combined, while still being a very low percentage of total US GDP historically and compared to other countries. There was no threat from communism, so if some Latin American countries wanted to experiment with it on their own, so be it, was the US foreign policy at the time.  President Obama would subsequently make statements to that effect when criticized why he wasn't more harsh with people like Hugo Chavez. But this was not the world in 1970 for a US seeing communism on a winning streak everywhere.