I think you don't need a escrow for this

Vietnam does not come under the AmazonGlobal program. You can order some of the product's from Amazon directly to Vietnam but not all of them.

There are many programs around the world which offer services for shipping parcels through private shipping companies from websites like amazon to any part of the world. One of the example is

https://usendhome.com
_{I cannot vouch of this, but still its legit}

This will help you in getting any of the product from amazon to reach your USA shipping address and than it will be re-shiped to the destination address in Vietnam.