Sorry, I meant to ask... totally skipped my mind. And I was in a room full of folks who would know...
Currently, afaik, it is not a released product in the USA. (Pretty awesome technology...)

I’ll ask, it’s in version 5 now and it is a very mature technology... and a very powerful tool.

Vocaloid was making some buzz with that keytar. Which, unless I'm missing something, doesn't sound like something I'd be asking to purchase. However, looking up "Vocaloid 5" - I find it's pretty much just software: https://www.vocaloid.com/en/ --- so I do not see what's keeping it from being purchased in the US.

I can go to that site, add Vocaloid 5 Premium to my cart, checkout, then pay (with Paypal) what they're asking for the Premium version. I assume you get a download link.

Unlike the keytar, Vocaloid 5 sounds great.

Intro: https://youtu.be/716cs27a6aQ
Detailed: https://youtu.be/UAtVGHl1AFM

so I do not see what's keeping it from being purchased in the US.

Support!

What I meant by:

so I do not see what's keeping it from being purchased in the US.

... was that I don't see what's keeping the OP from downloading the software from the website after paying with paypal. I didn't try - my assumption is that you actually can purchase this in the USA.

Which should have triggered me to ask: "did you try paying for the app, and were you not able to get a link after paying -- or did the site not accept your payment?"

Since I'm not in the market right now, I have no reason to test myself if I can spend ~$260 in order to provide a more definitive answer to my observation about not seeing what's barring someone from the USA from paying for this app online.

It looked like it might only be available as a Japanese version. I figured I'd ask before I leaped.

There are Japanese and English singers. I'm not sure what "only available as a Japanese version" means.

The interface demo'd doesn't look particularly Japanese. I think it localizes according to your OS.

Both versions available for purchase on the Vocaloid website show English and Japanese vocals. The Pro version just has more "characters" adding: CYBER DIVA II , CYBER SONGMAN II , VY1 , VY2 to the standard "characters": Amy , Chris , Kaori , Ken.

The Cyber (diva and songman) voices have demos online in English.

The video demos mainly seem to feature Sarah (English).

If you look at the demos - it shows pretty much what to expect. The demo is presented in English (narration) and the singing from Vocaloid is English.