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Why is only Japanese anime popular? Why don't other nations make anime as well?

This is a real no brainer, pal.
Look up the definition of ‘anime’.
One of the pre-requisites is that the Japanese or Chinese or Koreans are involved in its production.
Many ‘anime’ have been made in other countries. Totally Spies was made in Spain.
Code Lyoko was made in France.
Go way back to the silent film era in 1922- Prince Achmed was the first feature length anime film made using early sepia colurization screens.
The director was a woman and it was entirely filmed with a predominantly Japanese production team in Germany w/ an Austrian director! The dubbing of almost all anime is done in either Texas or Canada and of late, the UK and other parts of Europe.
However, in all fairness, the bulk of anime comes direvtly from Japna and the best of the lot is Japanese in origins. Many years ago Inferno based on Dante Alighieri’s Divine Comedy allegory was an anime film shot entirely in Italy.
You see, unlike live action films that need location filming to work, anime can be produced anywhere- even from an average home- house, condo, apartment, dorm room- as Toonami and Adult Swim have proven many times. Now here’s a bit of trivia you probably did not know re anime and amimation: Animation was created in the early 19th Century in Germany by an artillery officer to enable him to properly instruct his men in the use of a cannon! The famed ‘magic lantern’ invention soon followed. The very first anime was made during the Firt World War (1914–1918) in Japan long before Walt shared his lunch w/ Mortimer aka Mickey Mouse.
Steamboat Willie was not made until 1926.
Sadly, fire destroyed the only copies of this earliest anime filming. The only anime evr to win an Academy Award was Miyazaki’s delightfully refreshing anime film Spirited Away which took the Oscar away from Disney Studios several years ago when it won Best Animated Film of the Year! Unlike cartoons and other animation and puppetry, anime almost always has a plot, a few sub-plots, a theme and a storyline.
In addition, many anime are based on historical facts such as Rurouni Kenshin based on real life Japanese Samurai hero Kenshin Himura. Lastly, no other artform lends itself to the writing of fanfictions more so than doe s anime and where would the video game makers be w/o anime? Mortal Kombat began life as an anime film for example. The White Serpent was the first feature length talking anime film Dante and Virgil from the anime Inferno Rally Vincent drove a Shelby Cobra muscle car in Gunsmith Cats.
This car was the forerunner of the Ford Mustang and this short 3 episode anime series is what launched the popularity of both vehicles. Hayao Miyazaki now in his late 70’s is the only anime director to ever win an Oscar. Ebem amime characters sometimes celebrate our holidays.
Here Naruto and his Ninja pals have a Thanksgiving Day feast. The first usage of sepia colourization inn silent flms was done in 1922 w/ the silent anime film Prince Achmed which was shot in Germany, had an Austrian woman director and inspired the 1924, 1947 and 1961 Thief of Baghdad films. Rurouni Kenshin/Samurai X is based on real life Samurai hero Kenshin Himura who was beheaded for refusing to kill after vowing never to use his katana blade to take a human life again.
Instead he turned his katana’s blade over so the dull side was the leading edge thus vreating the sakabatou non-killing blade. Another period piece srt sometime following the 1601 Battle of Dekigahara at the Edo Castle in ancient Japan is Samurai Deeper Kyo. Spirited Away is a hauntingly beautiful fantasy film that remains the first and only anime film ever to receive an Oscar. In 1961 yet another version of Thief of Baghdad hit theatres.
Like all of its predecessors, this Steve Reeves vehicle (Steve is famous as Hercules in films; his brother George was TV’s first Superman) was also based on the 1922 silent anime film Prince Achmed.