Step 3: Here you see a registration form. Fill out the information. It is important that you at least fill in your real email address. The rest is not necessarily correct.
Step 4: In the 'country' you should not choose for the Netherlands (otherwise you pay shipping), but for the 'Cards'. This is also in the list. Click it.
Step 5: Enter a password and remember this!
Step 6: Click on continue. Your registration is complete and you've been automatically logged in. Go now to Step 7.
Step 7: Now you must choose a 20 PlayStation Network Card or a PlayStation Network 50 card.
(Tip: In the right menu you see 3 flags are. This is a list you can open. Click on the list and select 'Euro'. As you can see prices in Euros, and you see that it is a good price !)
Step 8: You have one (or more) of these PSN cards, click on 'Add to Card.
Step 9: Click on 'Check Out'
Step 10: Click 'Continue'
Step 11: Select a payment option, choose "PayPal."
Step 12: Click 'Continue'. Your order is confirmed, usually within an hour you will be your PSN card code received in your mail box.
Then you can redeem this code in the U.S. PlayStation Store through the Redeem Code option right at the top of the screen.
When you do this, you can spend the money on games that are available in the U.S. PlayStation Store. Good luck and have fun!
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Although I haven't done it myself, I would imagine if you used Japanese credentials then you could... but I recall reading that Sony checks/authenticates it so I don't believe you could use EU info to get things from the JP store.
If anyone else can clarify/confirm, it would be appreciated and I will +Rep ya!