Depends on the market for rhythm based games. A company attempting to sell and promote games that are not 'action' based have difficulties. A majority of views about the male gamer is that they won't buy games like Project Mirai and Diva due to the theme and content. In basic terms, too girly.
To save potential loss they(a company) simply won't export certain rhythm games by license. However, with Vocaloid becoming more known, there is a slim chance that Vocaloid games could be released to the USA market.