To me the fact that Ngram shows the word “patriotism” on the decline throws doubt on using it for any measure like this. Within the US “patriotism” is used very commonly. It leads me to wonder whether Ngram leans too heavily on scientific or academic literature and not on the words that people actually use in everyday conversation.

Does Ngram scan social media, TV or (to a lesser extent) newspapers? If not I’m dubious about the utility here.