The female school enrollment data is from https://data.worldbank.org/indicator/SE.SEC.ENRR.FE and the fertility data is from https://en.wikipedia.org/wiki/List_of_sovereign_states_and_dependencies_by_total_fertility_rate. The jupyter notebook can be seen at https://github.com/dbabbitt/StatsByCountry/blob/master/ipynb/Weekly%20Worship%20vs%20Fertility%20Rate.ipynb.

A low R-square of at least 0.1 (or 10 percent)is acceptable in the social sciences on the condition that some or most of the predictors or explanatory variables are statistically significant. So female school enrollment "explains" 67 percent of the variance in the fertility rate.

I threw a bone to those who use the mention of the United States as a soapbox on which to stand to trumpet their virtues. (They get a little anxious when they know one of those tiny dots is their target and they can't find it.) And, yes, the data for Puerto Rico is separate from the US data in both datasets. Thank you for noticing.