But Why
"Attention humans!" Celestia's voice boomed from every radio, speaker and television set on Earth. "Your time as an unforgivably violent and depraved species has come to an end! As we speak, our armies are marching towards your population centers and are prepared to face your leaders! You will convert to our side, or die!"
Thousands of armed ponies descended upon the north-eastern US coast, proudly waving the equestrian standard and forming battle lines as they prepared to march upon Washington. At their forefront were the Elements of Harmony, ready to face any threats.
On the opposite side stood the american army, steadfast and resolute even in the face of the approaching invaders. At their forefront stood Barack Obama, his ears flapping in the wind alongside the Stars and Stripes, alongside his trusted military advisor, the texan Six Thousand Star General Supreme Commander Proud Patriot American Eagle Jebediah "Lone Star" Granger.
"The enemy approaches," Obama muttered sullenly.
"Ain't no worries mister president sir," drawled Jebediah in his texan drawl as he put a comforting hand on Barack's shoulder before turning towards his troopers. "MEN! They may take our lives, but they will never take MUH FREEDOMS!"
The soldiers cheered loudly with whooping cries of "'MERICA!" before aiming their weapons at the oncoming army. Jebediah brought up his own gun - an AK16 firing six million rounds per minute fitted with a tactical ACOG red dot ballistic scope, a knife grenade launcher and a clipazine with infinite capacity for school-seeking bullets - before ordering the assault.
"OPEN FIYAH!"
The equestrian army started dropping like flies under the onslaught. In retaliation, several bolts of magic struck the patriotic men, who dropped on the ground with agonizing screams as a sorrowful trumpet played in the background. A single tear fell down Obama's cheek as a young kid fell at his feet, still proudly holding the tattered american flag high in the air.
"Tell mah ma', ah love her..." he gurgled out, but Obama firmly grasped his hand.
"Not today, son."
With his powerful ghetto magic, Obama tightened his hold on the kid as patriotic energies swirled around them. With a mighty cry of "CHANGE!", Obama infused the young man with so much freedom that all his wounds healed. The president helped the kid to his feet before raising a mighty finger towards the ponies.
"Onwards, my loyal men! Show them the superiority of your GENETICS!"
Suddenly, the ground started to shake as hundreds of 300-pound lardasses started rolling down the hill towards the Equestrian army, causing their ranks to scatter and flee from the oncoming disaster.
"YES WE CAN!"
Obama launched a powerful ball of energy towards the broken remains of the pony army, causing many casualties as they were overwhelmed with the superior american freedom that overshadowed the tyrannical rule of their royalty.
And thus, the few survivors were literally driven into the sea as they fled from the flood of fat still coming towards them.
Meanwhile, an elite pony task force led by princess Luna teleported itself into central London, with the goal of assaulting Buckingham Palace. All humans stopped in the street and watched as the princess halted a car and forced the driver to exit his vehicle.
"Tell me where your royalty resides, human, and thou might be spared!"
The driver stared at her silently for a long moment before opening his mouth filled with rotten teeth.
"ARE YOU WIMBLY FOURS MATE? IM CRIMBO NINAM SAX APPLE SMIBBLY DIN BIBBLY CHAP!"
Luna's expression changed from anger to sheer confusion. "I beg your pardon?"
"YOU WOT MATE?"
The ponies shuffled nervously as the man started laughing maniacally. Suddenly, everyone in the street froze as the Big Ben started ringing out. A carriage with the initials HRH rode across the street before stopping in the middle of it, and the queen of England herself stuck her head out.
"OI YOU GITS DID YE HEAR THAT!? IT BE SIX BONG!"
The driver poked his head out. "SIX BONGERS?"
Luna fell backwards as the sewer cover under her burst open and another filth-covered man jumped out. "SIX FECKING BONG?"
The princess and her guards soon found themselves almost crushed by the sheer mass of people that started pouring out into the street. "YA WANKERS IT BE CRIMBO SIX-A-BONG!" She heard someone shout.
Store clerks and chimney sweepers started dancing around, chanting "SIX-A-BONG, SIX-A-BONG" as Luna and the ponies started choking from the amount of filth in the air.
"SIX-A-BONG, SIX-A-BONG, OLLY JOLLY IT'S SIX-A-BONG!"
Luna screamed in frustration as she felt herself being carried way by the unavoidable crowds of chanting dancers as copious amounts of fish and chips were thrown in the air. "BANG UP THE KNACKERS AND SMACK YER MUM, OLL IN THE STREETS IT'S SIX-A-BONG!"
Meanwhile in Australia, Tony Abbot was having a fistfight with a the owner of a bar about which flavor of vegemite was superior. The commotion was interrupted as an australian secret service agent announced the ponies' arrival by trumpeting on his royal didgeridoo. Silence settled over the patrons before Tony Abbot smashed a beer can against his own head.
"Fockin 'ay, whot a buncha' fukken KUNTS!"
As civilians started packing their cane toads and vegemite tubes and started heading for safety in the Outback, Tony Abbot ordered in the "Dream Time Brigade": a task force of aboriginal and australian hunters trained in the art of gun and blade.
Meanwhile, the pony fleet led by Cadence and Shining Armor arrived at the Australian Coast. As Shining ordered the humans through his magical megaphone to stand down, silence reigned across the ocean as everyone awaited Abbot's response.
"Yeah, nah, you're a shit cunt."
"Very well then."
Shining lent closer to his wife and whispered in her ear: "I have no idea what he just said."
As the mainland invasion force set hoof on australian soil oblivious to their fleet being eroded away by australian sharks, they were engaged by aboriginals hurling burning oil drums at them while hollering in their native language. The invasion force was soon overwhelmed by mounted emu and kangaroo troopers mowing them down on each pass, and australian hunters skinning their pelts to sell to the Japanese.
Back in Canterlot, a princess with disheveled hair watched in utter disbelief as her ponies were driven away from every part of the planet. Western Europe had been a complete failure from the start, as her guards were mercilessly beaten to death either by baguette-wielding frenchmen shouting "A-hon-hon-hon" or german über-brätwürsts. Russia had ended in catastrophe as her forces were drowned in seas of vodka and burly slavic men yelling "CYKA" at every inopportune moment, and her ponies in China and Japan were never heard from again as they disappeared in the morning rush crowds to the subway.
Celestia's eye twitched as she took in the full scope of the situation.
"...Well shit."