Since I am not an American I can speak for all the rest of us!! You state that 'America' (by which I presume you mean the United States thereof, and not the countries to the north and south who also inhabit that part of the world known as America) believes in both Evolution and Creation. And here is where it all gets a bit complicated. You see I 'believe' in neither, and this is where the crucial aspect of 'America's' belief system impinges on scientific fact.

In order to 'believe in Creation' it is necessary to believe in God, or at least a supernatural being who made heaven and earth, or if you are more trendy designed the Universe. Every society in the ancient world had its creation myth and the one that is cherished by those who 'believe in Creation' is the myth of the early Jewish civilisation, via Ancient Egyptian texts-- and bit of general middle eastern legends thrown in too. The thing is that in the US more people believe that this myth really is the way life began than most people in the rest of the world. This difference is, in my opinion, due to the fact that religion and church generally is still important in a way that it is not in for eg, in my country, where politicans are unafraid to affirm an oath of office instead of swearing on a holy text. They do this without fear of offence.

To get back to Evolution. No one 'believes' in Evolution. It maybe that people believe in the ability of the idea to encompass much of the previously unknown facts of life's origin has been sustained, and it is able to absorb the new discoveries without having to invent flights of fancy to explain new discoveries. Until a better theory comes along, this one is doing fine. But it is not a 'belief'. A true belief requires faith, but not necessarily truth.

So some of 'America' does believe in Creation, but some others accept the Theory of Evolution as being a more empirical truth.