Ayu would have to have a very small venue in order to sell all the tickets. I truly don't think enough people would go. Maybe she could in the 2000s but no way now. Ayu doesn't have a good image in the US at all sadly. People have either forgotten her, don't even know who she is, or think she is washed up and has a terrible voice.
As much as I want her to come do a tour here, I think it would only hurt her in the end. It would spark conversation of Ayu versus Utada, her vocal performance will definitely have many critics, it may hurt her image if not enough tickets are sold as well. Giving more proof to the haters that Ayu's career is over.
What Ayu could have done is, back in the early to mid 2000s she could have performed Dearest at anime conventions across the country. That is what she is most known for here anyway. But it is too late now.