"Jesus warned in the 24th chapter of Matthew that in the last days we would see 'nation rising against nation and kingdoms rising against kingdoms.'”:

In the Greek the phrase is "ἐγερθήσεται γὰρ ἔθνος ἐπὶ ἔθνος", "For nation will rise against nation…", where "nation" is ἔθνος ("ethnos"). This is not necessarily exactly the same idea as what we think of with the English word "nation". I don't have a commentary reference for this, but when I see a scripture like this I tend to think in terms of the "Table of Nations" in Genesis 10. In the Septuagint (Greek Old Testament) the same word is used.

The word for "will rise", ἐγερθήσεται ("egerthēsetai") apears in the 3rd person singular future passive indicative. It is singular because ἔθνος is singular, but why passive? I'd guess it is nuance, though.

BDAG defines the word ἔθνος in the context of Mt. 24.7 as "1. a body of persons united by kinship, culture, and common traditions, nation, people". There is also this remark in NIDNTT, "2. In about 100 instances ethnos is used in contrast to the followers of Jesus … One of the horrors of the end time will be the rising of nation against nation (Matt. 24:7)."

Horror indeed. Mathew might have had this kind of meaning in mind, which is more specific than our word "nation" would imply. These "nations" or peoples still exist, and they are very much in the news, and rising up against each other. They appear to be quite resilient.