godzilla 1984 american or japinese ?

Yep, both USA and USSR Wanted to nuke japan with all of their nuclear weapons to get rid of godzilla. Still didn't happen though.

The giant leeches have different sounds of their somewhat skreeches.

Professor Hayashida confronts the sole survivor of the ship wrecking and shows him pictures of godzilla from 1954.

Professor Hayashida actually studies the generics of the vinager fly instead of the genectic mutations.

"is there a big differance"

Good lord, yes. They're pretty much two different movies. I don't think I could name all the differences by memory.

Along with everything BBB said a few of the scenes with Godzilla attacking are switched around. They are fairly different I would recommend seeing both as both have their merits.

Biggest diffenece is the whole Cold War aspect in the moive.

Dear God... The Return of Godzilla and Godzilla 1989 are essentially two completely different motion pictures.  The best way to tell the difference is that The Return of Godzilla makes sense, is entertaining, and can be taken seriously.  The American cut was camped up in the extreme, with insensitive, unfunny dialogue written for the scenes with the english cast, and the Russions were turned into overt villains by editing, cuts, and false subtitles.  If you want a version to watch, track doen the Japanese version... its out there for the watching. :)

For a complete list of all the differences (which I know all of, but am too lazy to type out), check out this article on Tohio Kingdom:

http://www.tohokingdom.com/articles/art_toho_in_america.html

Just scroll down and you'll find the entry on The Return of GOdzilla/Godzilla 1985. :)