Why are Creationism and Evolution such controversial topics in the U.S. today ?
Quite simply, ignorance. A large body of people are under the impression that the Theory of Evolution is somehow Un-Christian or that it in some way attack the concept of the existence of GOD. That is simply a false statement and belief, and is countered by the evidence at hand. Whenever the issue of Creationism and the Theory of Evolution comes before the public, the vast majority of opponents to the idea of teaching Creationism are Christian and Judaeo-Christian-Islamic Theologians.
For more information I suggest you look at the lists of groups who have testified at the various times the issue has been discussed publicly. You could begin by reading of The Significant Court Cases dealing with this issue.
But YOU need to do the research and form your own opinions on the matter. Don't try top get the folk here to do your homework. We can point you towards sources but YOU must do it yourself.
Strat by doing a web search for the position papers of the major Christian sects on this issue.