Learning American vs Japanese art

Manga/anime artists seem to have a firm grasp of style, anatomy, angles, movement, expression, action, etc.  You can usually tell when an artist is bad for not getting basic principles.  US art doesn't seem as structured- styles can go in any direction.  Is there a reason behind this?  Are there art schools in Japan that teach manga style more, or at an early age?  How are the basics of art learned differently than in the US?

Hmm, it's not like everyone in japan know anatomy perfect. Manga and such exists side by side as a part of their culture so if people doodle at an early age its nothing much if they dont continue to deveop themselves.
The question is, is US comics a equally big phenomenon as manga is in Japan?

First of all, there is a lot of Japanese manga artwork that I wouldn't consider to be all that great. But unlike Japanese manga artists, who learn all of the things you listed above, and then stylize, U.S. artists forego the basics, and just use "style" as a crutch to hide their lack of knowledge in these areas.

I don't know how it is in Japan, but here in the U.S., a lot of people who consider themselves to be good artists, whether self-proclaimed, or even coming from an art school or having/working on an art degree don't know the basics, especially when it comes to human form, or organic-looking subjects in general.

No, but there are a lot independent comics below the spotlight of the major publishers- only a few get enough fans to survive.  The use of advanced coloring techniques makes mainstream comics more appealing but more costly, meaning there's less black and white stories to be supported as everyone sticks to reading X-men instead.  With manga, only a couple pages are in full color unless it's a full color special, but usually everything is black and white. 

Then the question is, how is it in Japan?

im no art expert, but i agree with the theory that most things japanese are deeply rooted in 'kata' or 'the way' of doing things. To not make this post too long i will just explain that each and every thing Japanese do has a certain or set way to do a certain task. And that all Japanese follow this certain way for the given task, since 'kata' hasbeen ingrained in their culture for over centuries.

so when japanese go to art school and learn to draw they learn the basics and 'the way' of drawing. Then later after they finish school they go off on their own ways to make their drawings stylish and unique. And i think that explains why most of the anime/manga in japan isn't as diverse as it is in America.
 

All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy