I do not think you can attribute that just to propaganda...For example, Soviet block countries were among most heavily propagandized, yet large segments of the public was not receptive to this particular propaganda claims. In other words, we need to focus not just on what is being said, but also on what is being heard.
My own view of the issue is that the receptiveness to corporate propaganda in the US has two roots. The first one is anti-intellectualism...
The second root is that in the US, much more so than in most other countries, media consumption (radio, tv) tends to be a solitary rather than a collective activity...As a result, the media contents is likely to be socially mediated and interpreted than in other countries, and thus taken for its face value.
In short, the US is probably the most propagandized society on the face of the earth - but that is a result of social structure and social belief system more than the mere effectiveness of propaganda. ================================= I'd add a poisonous combination of racism and stagnating real incomes to the cultural factors identified by Wojtek. Many white working and lower middle class Americans seem to believe government spending is primarily aimed at blacks and immigrants and this, coupled with their inability to augment their incomes in the workplace or through self-employment, encourages them to seek relief through lower taxes and draws them into the conservative Republican orbit.
This process has been underway within the white working class since the civil rights movement of the 60's and the relative decline of US manufacturing over the ensuing three decades. The election of Obama, seen as a representative of the black community, and the financial crisis resulting in a massive decline of US household assets and the dramatic expansion of the federal deficit with it's implicit threat of higher taxes, has lent it powerful impetus - with the health care issue serving as the lightning rod.