Generally speaking, people favor or oppose abortion because of the influence of secularism or lack thereof. This is true in countries besides the US as well, including ones with few Catholics or Evangelicals or even that are mostly non-Christian. I think it's a perfectly legitimate way to point out how Evangelicalism in the South has really taken off in the last 30 years.
http://www.washingtonpost.com/blogs...s-complicated/2012/05/29/gJQAjj0qyU_blog.html
But such interpretations raise the question of whether these binary, politicized labels accurately capture Americans’ nuanced views on abortion. Last summer, a major national survey by Public Religion Research Institute uncovered a surprising but critical feature of the abortion debate: 7-in-10 Americans reported that the term “pro-choice” described them somewhat well (32 percent) or very well (38 percent), and nearly two-thirds simultaneously said that the term “pro-life” described them somewhat well (31 percent) or very well (35 percent). In other words: when they were not forced to choose between one label and the other, over 4-in-10 (43 percent) Americans said that they were both “pro-choice” and “pro-life.”
These overlapping identities are present in virtually every demographic group. For example, it is true of Democrats (56 percent “pro-life”; 81 percent “pro-choice”), Independents (66 percent “pro-life”; 73 percent “pro-choice”), and Republicans (79 percent “pro-life”; 52 percent “pro-choice”).
Among religious groups, with the exception of white evangelical Protestants, solid majorities of every major religious group say both terms describe them at least somewhat well. And even in the case of white evangelical Protestants, although two-thirds (67 percent) say abortion should be illegal in all or most cases and 8-in-10 (80 percent) say that the term “pro-life” describes them at least somewhat well, nearly half (48 percent) nonetheless identify as “pro-choice.”
That hardly sounds like something as neat and tidy as "the influence of secularism makes people pro-choice."
I'd be happy to accept that evangelism in the South has taken off in the last thirty years, but trying to tie attitudes on abortion to attitudes on secularism isn't very convincing.