In the early 1930s, including his time spent in Lecumberri Prison, Siqueiros produced a series of politically themed lithographs, many of which were exhibited in the United States.
His lithograph Head was shown at the 1930 exhibition "Mexican Artists and Artists of the Mexican School" at The Delphic Studios in New York City.
In 1932, he led an exhibition and conference entitled "Rectifications on Mexican Muralism" at the gallery of the Spanish Casino in Taxco, Guerrero.
Shortly after, he traveled to New York, where he participated in the Weyhe Gallery's "Mexican Graphic Art" exhibition.
Also in 1932, Nelbert Chouinard invited Siqueiros to Los Angeles to conduct mural workshops.
It was at this time that, with a team of students, he also completed Tropical America in 1932, at the Italian Hall at Olvera Street in Los Angeles.
Painting fresco on an outside wall – visible to passersby as well as intentional viewers – forced Siqueiros to reconsider his methodology as a muralist.
He wanted the image – an Indian peon being crucified by American oppression – to be accessible from multiple angles.
Instead of just constructing "an enlarged easel painting", he realized that the mural "must conform to the normal transit of a spectator."
Eventually, Siqueiros would develop a mural technique that involved tracing figures onto a wall with an electric projector, photographing early wall sketches to improve perspective, and new paints, spray guns, and other tools to accommodate the surface of modern buildings and the outdoor conditions.
He was unceremoniously deported from the United States for political activity the same year.

Back in New York in 1936, he was the guest of honor at the "Contemporary Arts" exhibition at the St. Regis gallery.
There he also ran a political art workshop in preparation for the 1936 General Strike for Peace and May Day parade.
The young Jackson Pollock attended the workshop and helped build floats for the parade.
In fact, Siquieros has been credited with teaching drip and pour techniques to Pollock that later resulted in his all-over paintings, made from 1947 to 1950, and which constitute Pollock's greatest achievement.
In addition to floats, the Siqueiros Experimental Workshop produced a variety of posters and other ephemeral works for the CPUSA and other anti-fascist organizations in New York.
These ephemeral works possessed the ability to reach the masses in a way different from mural painting because they were accessible to a wide audience outside of an institution or gallery.
The Siqueiros Experimental Workshop only lasted for a little over a year until Siqueiros went to fight in the Spanish Civil War in April 1937, but their floats were featured in both the 1936 and 1937 May Day Parades in Manhattan's garment district.

Continuing to produce several works throughout the late 1930s - such as Echo of a Scream (1937) and The Sob (1939), both now at the Museum of Modern Art in New York – Siqueiros also led a number of experimental art workshops for American students.
He spent the better part of 1938 with the Spanish Republican Army fighting Francisco Franco's fascist coup before returning to Mexico City.
After his return, in a stairwell of the Sindicato Mexicano de Electricistas, Siqueiros collaborated with Spanish refugee Josep Renau and the International Team of Plastic Artists to develop one of his most famous works, Portrait of the Bourgeoisie, warning against the dual foes of capitalism and fascism.
 The original mural shows a giant generator using the opposition of fascist and capitalist democracies to generate imperialism and war.
An armed, brave-faced revolutionary, of unnamable class or ethnicity, confronts the machine, and a blue sky on the ceiling flanked by electrical towers displays hope for the proletariat in technological and industrial advances.
In the early 1930s, including his time spent in Lecumberri Prison, Siqueiros produced a series of politically themed lithographs, many of which were exhibited in the United States. His lithograph Head was shown at the 1930 exhibition "Mexican Artists and Artists of the Mexican School" at The Delphic Studios in New York City. In 1932, he led an exhibition and conference entitled "Rectifications on Mexican Muralism" at the gallery of the Spanish Casino in Taxco, Guerrero. Shortly after, he traveled to New York, where he participated in the Weyhe Gallery's "Mexican Graphic Art" exhibition. Also in 1932, Nelbert Chouinard invited Siqueiros to Los Angeles to conduct mural workshops. It was at this time that, with a team of students, he also completed Tropical America in 1932, at the Italian Hall at Olvera Street in Los Angeles. Painting fresco on an outside wall – visible to passersby as well as intentional viewers – forced Siqueiros to reconsider his methodology as a muralist. He wanted the image – an Indian peon being crucified by American oppression – to be accessible from multiple angles. Instead of just constructing "an enlarged easel painting", he realized that the mural "must conform to the normal transit of a spectator." Eventually, Siqueiros would develop a mural technique that involved tracing figures onto a wall with an electric projector, photographing early wall sketches to improve perspective, and new paints, spray guns, and other tools to accommodate the surface of modern buildings and the outdoor conditions. He was unceremoniously deported from the United States for political activity the same year.
Back in New York in 1936, he was the guest of honor at the "Contemporary Arts" exhibition at the St. Regis gallery. There he also ran a political art workshop in preparation for the 1936 General Strike for Peace and May Day parade. The young Jackson Pollock attended the workshop and helped build floats for the parade. In fact, Siquieros has been credited with teaching drip and pour techniques to Pollock that later resulted in his all-over paintings, made from 1947 to 1950, and which constitute Pollock's greatest achievement. In addition to floats, the Siqueiros Experimental Workshop produced a variety of posters and other ephemeral works for the CPUSA and other anti-fascist organizations in New York. These ephemeral works possessed the ability to reach the masses in a way different from mural painting because they were accessible to a wide audience outside of an institution or gallery. The Siqueiros Experimental Workshop only lasted for a little over a year until Siqueiros went to fight in the Spanish Civil War in April 1937, but their floats were featured in both the 1936 and 1937 May Day Parades in Manhattan's garment district.
Continuing to produce several works throughout the late 1930s - such as Echo of a Scream (1937) and The Sob (1939), both now at the Museum of Modern Art in New York – Siqueiros also led a number of experimental art workshops for American students. He spent the better part of 1938 with the Spanish Republican Army fighting Francisco Franco's fascist coup before returning to Mexico City. After his return, in a stairwell of the Sindicato Mexicano de Electricistas, Siqueiros collaborated with Spanish refugee Josep Renau and the International Team of Plastic Artists to develop one of his most famous works, Portrait of the Bourgeoisie, warning against the dual foes of capitalism and fascism.  The original mural shows a giant generator using the opposition of fascist and capitalist democracies to generate imperialism and war. An armed, brave-faced revolutionary, of unnamable class or ethnicity, confronts the machine, and a blue sky on the ceiling flanked by electrical towers displays hope for the proletariat in technological and industrial advances.
David Alfaro Siqueiros