it should be fine - i am going to repeat the process so my 16 gig is fine for US content today.
1) Factory restore JPN PSV with the 16 gig card in (US target card)
2) opt to DEACTIVATE account when asked
3) Input US account details
4) watch that F***ing intro movie AGAIN
5) Download content from PS3 to PSV
6) Factory restore US PSV with 32 gig card in
7) opt to deactivate US account
8) input JPN account details
9) Wave fist at the stupid intro movie AGAIn
10) Check i can still play content from mem card
11) victory
12) make months of posts moaning that the process wouldn't be so bad if it wasn't fot having to watch the stupid intro Movie
.
So that means you can play stuff off JP PSN on a US account afterall?