Haven't tried this but it might work.

Go to the English Youtube and copy the URL.

Clear your Cookies.

Now open up your browser and PASTE the URL.
He tried that Carbon, even used the IP address to by-pass any hosts file or DNS re-directs.

Bish, do you have the 'use proxy server' box ticked in your browser settings, perhaps your ISP Proxy Server is doing it?
IE>Tools>Internet Options>Connections.

As a test did you TRY using a third party proxy server to get a different IP address?

I WOULD have thought that by using the US IP address would get you to the US site no matter what, someone is re-directing you but who?
Your own computer > your ISP, the CIA, the US site?

I'm in Oz and if I put in http://www.google.com (US) I get sent to http://www.google.com.au (AUST) but if I put in http://209.85.171.147/ (US) I go to the US website.

I know you're not concerned about Google but thought I'd add it to see if it would help throw some light on this problem.

Blast your ISP, tell them when you type www.blahblah.com that's where you want to go not www.blahblah.com.japan.
Belt your fist on the table. Simply out of curiosity...
Go to C:\WINDOWS\system32\drivers\etc and open your hosts file in Notepad.  Can you copy/paste the contents here for us?