There are ... were only a couple of options for the AirForce at the time... one a missed opportunity a few years back with the C-17 Whitetails and the A400m which in reality is behind schedule and has had a few mishaps along the way.
Is the C-2 capable... ???? not sure
The C-2 is capable and more comfortably so than the A400M. I was given some aircraft hold data a while back and haven't found my record of the source details for it yet, but it is legit.
You can see from the above table that the C-2 hold is 15 cm higher than the A400m. Mightn't sound much but makes a difference.
Copied a screen grab off an Airbus Video. As you can see not a lot of room especially at the top. This screen grab didn't show very good detail of the rotor head relative to the aircraft deckhead, so I got my own screen grab from the video (link posted below).
As you can see, it appears that the rotor head hasn't been removed, but the head cover has, unlike when the NH90 have been transported by the C-17 as per
the photo in my post (#8064) 2 days ago.
The video is below for those interested.