I have no idea if this was relevant to the issue, but to reduce the chance of your address getting messed up, make sure it passes the USPS online verification. Otherwise when the seller tries to print the shipping label they'll end up trying to figure out how to edit the address to get it accepted. That can be confusing when shipping overseas.
I used to get frustrated with addresses when shipping to Puerto Rico, whose addresses are very different from what I'm used to in the 50 states. They're also longer, and often don't fit in the character limits imposed. At some point USPS verification started working a lot better with PR but it used to be awful.
I also had a verification issue once with the UK, where it turned out the town name given by the seller was obsolete. After some research I found that there was a political controversy about the name of the town/district/whatever, and using the wrong name might lead to mail being angrily rejected. Sheesh.
A seller really should know better than to pack a CPU like that. I guess they haven't done it very many times - you're providing their learning experience, unfortunately. They should also know better than to take any chances with international mail. If it's possible for a package to get abused, it's more likely to happen with international than in any other situation. I will add though that if you're concerned and want to discuss packaging or other details with a seller, the most proper time to do it is before purchase, not after. It can be frustrating to get special requests after something has been bought and an obligation has been established to ship in a set timeframe for a set price (depending on how specific the request is, of course). There's also the risk that the seller won't see the message, they'll just go to work shipping it per their routine.
A few years ago I remember buying something on eBay and the seller (domestic) handwrote the address. They managed to misspell the town name, mangle the zip code, and mangle the house number. Truly amazing. Even more amazing is that it still got delivered to me.