Eyeglasses were invented by Salvino D'Armate in 1282.
There are no flights from Frankfurt to Stuttgart, the distance is too small.
The priest is the only German who actually speaks authentic German without a foreign accent, but strangely, not all the time. When talking to the sacristan and the henchmen, his speech becomes stilted, with exaggerated enunciation.
The "German" airport announcement on the Tannoy is an unidiomatic literal translation and delivered in a thick American accent. Specifically, an airport gate is called a "gate" in Germany as well, not a "Schanze".
Nick and Monroe's itinerary takes them from PDX->FRA->STR. Their passports are stamped in Stuttgart, but when entering the Schengen country, one clears immigration at the first point of entry, and thus they would've cleared immigration at Frankfurt.
Just because the church was built after the crusades doesn't have to mean they are in the wrong place. Many European churches were built on top of the ruins, foundations or crypts of older churches, which Monroe should know.
The mere fact that a European church is Protestant does not mean it wasn't built before Martin Luther's time and before the reformation. Many Catholic churches were converted during and after the Reformation along with their congregations, be it peacefully or during any one of Europe's many religious wars. Which Monroe should know.