So do you think that one day in 476 AD (CE for my progressive but misguided friends) the Goths rolled into Rome, sacked the place, had everyone hang up their togas and started speaking German within a week or so? Not so much.
Let's go back to 69 AD aka the Year of the Four Emperors. This is the first - but not the last -- civil war in the newish (27 BC) Roman Empire. We have the Year of the Five Emperors in 169 AD and it just goes on with disagreements, power grabs, and wars pitting legion against legion, literally bleeding the strength of the nation.
As legions diminished their ranks were supplemented by non-Romans and then replaced by entire foreign armies as mercenary forces.
Alaric , the kind of the Goths, who sacked Rome in 410 had long served in the Roman military under Theodoius, mainly fighting the forces of usurpers.
Fast forward
In 1204 the Fourth Crusade was on the way to the Holy Land from western Europe but made a detour to Constantinople, seat of the still standing Eastern Roman/Byzantine Empire . The pillage and destruction of the seat of Orthodox Christianity by Catholic Christians forever weakened the city so that in 1453 it finally fell to the Ottoman Turks.
Next stop North America
You will recall -- as apparently a paltry few current 8th graders now know -- that the French & Indian War was not a conflict pitting French soldiers against Native Americans. It was the French vs the English in 1754 with some tribes siding with the English and others siding with the French (incidentally the larger world-wide conflict known as the Seven Years Wars was fought globally from India to North America to Europe).
Back to Italy
About the time the Mexicans were defeating a French army fighting for a Hapsburg emperor (Cinqo de Mayo) and Jefferson Davis was having terse talk with Abraham Lincoln, the Italians were just getting together. Yes, Italy as a country was only founded in 1861 under Garibaldi. For several hundred years prior the competing city-states - Milan, Florence, Venice, etc - fought each other and were at various times under the control of France, Spain, and others.
So what
What is the common thread? Division within invites conquest from outside.
Do you really want to have to learn to speak Chinese?
It is troubling that left- right, progressive- conservative, urban- rural, etc can't seem to agree on anything at all, but part of that (not all but part) is from an unwillingness to even try. How do you think this will play out in the long run?
P.S. In Rome under Odoacer who deposed the last child emperor in 476 and declared himself king of Italy, some things went on as usual -- the Roman senate continued, coinage, even the Latin language. Many changes were gradual but the movement toward instability and lack of security accelerated over time.
