Hmmmm well i think it would be great if Ayu simply did an international tour, i'd be wayyy up for that.
But English album.. not sure, I think we should trust that Ayu will make the best decision for her, she and her team are not stupid, i think thats why she hasn't released in the U.S. before. Seriously though, so what if she tries and fails, its all a learning experience etc etc.
On another note, in the alternative scene, various overseas acts have made a moderate success, such bands as Shonen Knife were played on the radio and performed at touring festivals in the 90's here in Australia.
Also its all about promotion, and working at it! Neither Utada or BoA have promoted themselves enough! They need work and work, release heaps of singles and most importantly music videos (as pop music has become mostly visual medium in the last 10 years) until they finally break though, its ridiculous to think that releasing one single they will make it huge immediately.. rarely any U.S artists even do that.
Anyway in conclusion, whatever Ayu chooses to do, i support it!