It is really hard to talk about "America's" attitude on this because different parts of "America" would have had very different attitudes. In general, though, the attitude was very anti-civil rights in the white South and fairly uninterested in the North about the issue.
By 1955, there had not been any of the protests that would later make this an important issue in the North. The South cared about it to some extent, as can be seen in the formation of the "Dixiecrats" who ran Strom Thurmond for president on a segregationist platform in 1948. This was done mainly in response to moves to integrate the armed forces. Again, however, this was not a salient issue in the North.
The Brown v. Board decision had been handed down in the 1954, and that caused opposition in the South, but no actual attempts had been made to integrate by 1955 and so that issue was still largely unimportant.
Overall, then, the attitude towards civil rights in the US was very negative in the South and generally uninterested in the North in 1955.