Biden to meet with Pope to discuss climate change, global taxation, And Covid-19, amongst other political issues….what happened to separation between church and state?

I might be especially smooth brained (and this question is more rhetorical I suppose), but why on earth is the Pope solicited for any political issues? Did the church finally decide that they should pay taxes? Or is this meeting to figure out a way for them to evade the new global tax they’re trying to push, too?