can iTunes US account buy things while you're staying oversea

yes, you just have to browse the US itunes store. you can change your store in the bottom right of the itunes store window.

correct

Hi,

It is not that simple! You will need to have a credit card issued in the country that you visit in order to use that countries store. In any event, you will be able to use your US account to buy things from US store.

Jim

Still not that simple (well it is, but the previous answers haven't been completely correct)!

The iTunes Store in a country is intended only for use by that country's residents, and only while they are in the country. To use the iTunes Store in a country you need a credit card (or other card type if acceptable in a country) issued in that country, billed to an address in that country, and also be physically present in that country when using the store. You are also restricted to waiting 90 days between country changes. Put simply, you can only use the US Store with a US registered account.

E.g., "The iTunes Service is available to you only in the United States, its territories, and possessions. You agree not to use or attempt to use the iTunes Service from outside these locations. Apple may use technologies to verify your compliance." - http://www.apple.com/legal/itunes/us/terms.html#SERVICE - Simply put, you are not supposed to even try to use the US store when in another country. You may find Apple blocks you from trying.

If you are moving outside the USA and taking up residence in another country (not just visiting) you can change the country for your AppleID. As noted earlier you also have to set up valid payment for that country too. Even if you create a new AppleID you will still need an address and a credit card for the other country. You don't want multiple AppleIDs anyway because it gets messy trying to authorize items on one computer.