One problem that Objectivism runs into right from the start is the near universality of religion. We find it nearly everywhere, even among isolated peoples. If religion were merely a product of premises, we would expect to find more variety in the world at large, as some cultures would choose religious premises and hence become religious, while other cultures would choose non-religious premises and hence become secular. Moreover, since religion (at least according to Objectivism) is "irrational," and since the irrational is impractical and even "evil," we would expect non-religious cultures to have a competitive advantage over religious cultures, so that over time, the non-religious, through a kind of natural selection, would triumph over and replace the religious. Oddly enough, this has not happened.
There is one major exception to the universality of religion: contemporary Europe. Soviet Russia and communist China could also be seen as exceptions as well, except for the fact that religion was brutally repressed in those countries, and that communism itself is a sort of secular religion. Europe, however, is one example that might fit within Rand's theory. The problem is, it might not fit. There may exist special circumstances in Europe which enable the natural proclivities toward religion to be supressed. After all, if Europeans have chosen non-religious premises, there must be a reason for this. While Objectivism often ignores the whole issue of why individuals in a special set of circumstances might choose one premise rather than another, it nonetheless would appear an important question to address if one is interested in discovering the truth of the matter.
In the United States, religion still remains a fairly strong force. More than half of Americans attend church at least once a month, and more than a third attend church once a week. Over three-quarters of Americans identify themselves as Christian. Nonetheless, 20% of Americans never attend church, and another 25% "seldom" attend church. Oddly, church attendance rose in the weeks following the 9/11 terrorist attacks, but returned to pre-9/11 levels within two months. This suggests that religiousity increases, not as a result of any inexplicable or causeless acceptance of "religious" premises, but because many (perhaps even most) people are hardwired to turn to religious constructs when they feel seriously threatened. It might very well be that Europe is predominantly secular and non-religious because Europeans are wealthy and they feel safe. Take away the wealth and the safety, and Europe would return to religion (or the secular equivalent thereof).