・プログラムコードは、日本版のものをほぼそのまま流用

AWSの仕組みは各国共通です。素晴らしい！
ただし、データーの呼び出し先は「http://webservices.amazon.co.jp/onca/xml?〜」から「http://webservices.amazon.com/onca/xml?〜」へ変更になります。他の国でも同様です。

・Asoociate IDは各国版のものを取得する

日本のAmazon.co.jpで取得したアソシエイトIDは、海外では利用できません。

USAはこちらからです。指示（英語ですが多分わかります）に従って必要事項を記入します。
USAの場合IDが「hogehoge-20」となります。（日本は「hogehoge-22」）
報酬の支払いは、Check(小切手)かAMAZONの商品券しか選択できないようです。

・sort項目がSearchIndex毎に細かく異なるので、注意が必要

プログラムを組む際、各SearchIndexごとにsort項目を変更する必要が出てきます。

PHP用の配列を紹介しておきます。
もし間違いや変更があれば、教えていただけると嬉しいです。

$sort_a['Apparel']=array('relevancerank'=>'Best score','salesrank'=>'Bestselling','pricerank'=>'Price: low to high','inverseprice'=>'Price: high to low','-launch-date'=>'Newest arrivals','sale-flag'=>'On sale'); $sort_a['Automotive']=array('salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A'); $sort_a['Baby']=array('psrank'=>'Best score','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z'); $sort_a['Beauty']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','-launch-date'=>'Newest arrivals','sale-flag'=>'On sale'); $sort_a['Books']=array('relevancerank'=>'Best score','salesrank'=>'Bestselling','reviewrank'=>'Average customer review','pricerank'=>'Price: low to high','inverseprice'=>'Price: high to low','daterank'=>'Publication date','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A'); $sort_a['Classical']=array('psrank'=>'Best score','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A','orig-rel-date'=>'Release date'); $sort_a['DigitalMusic']=array('songtitlerank'=>'Most popular','uploaddaterank'=>'Date added'); $sort_a['DVD']=array('relevancerank'=>'Best score','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-video-release-date'=>'Release date'); $sort_a['Electronics']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z'); $sort_a['GourmetFood']=array('relevancerank'=>'Best score','salesrank'=>'Bestselling','pricerank'=>'Price: low to high','inverseprice'=>'Price: high to low','launch-date'=>'Newest arrivals','sale-flag'=>'On sale'); $sort_a['Grocery']=array('relevancerank'=>'Best score','salesrank'=>'Bestselling','pricerank'=>'Price: low to high','inverseprice'=>'Price: high to low','launch-date'=>'Newest arrivals','sale-flag'=>'On sale'); $sort_a['HealthPersonalCare']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','pricerank'=>'Price: low to high','inverseprice'=>'Price: high to low','launch-date'=>'Newest arrivals','sale-flag'=>'On sale'); $sort_a['HomeGarden']=array('salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A'); $sort_a['Industrial']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A'); $sort_a['Jewelry']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','pricerank'=>'Price: low to high','inverseprice'=>'Price: high to low','launch-date'=>'Newest arrivals'); $sort_a['Kitchen']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A'); $sort_a['Magazines']=array('subslot-salesrank'=>'Bestselling','reviewrank'=>'Average review','pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A'); $sort_a['Merchants']=array('relevancerank'=>'Best score','salesrank'=>'Bestselling','pricerank'=>'Price: low to high','inverseprice'=>'Price: high to low','-launch-date'=>'Newest arrivals','sale-flag'=>'On sale'); $sort_a['Miscellaneous']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A'); $sort_a['Music']=array('psrank'=>'Best score','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A','artistrank'=>'Artist name: A to Z','orig-rel-date'=>'Original release date','release-date'=>'latest release date'); $sort_a['MusicalInstruments']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','-launch-date'=>'Newest arrivals','sale-flag'=>'On sale'); $sort_a['MusicTracks']=array('titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A','artistrank'=>'Artist name: A to Z'); $sort_a['OfficeProducts']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','reviewrank'=>'Average review','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z'); $sort_a['OutdoorLiving']=array('psrank'=>'Best score','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A'); $sort_a['PCHardware']=array('psrank'=>'Best score','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z'); $sort_a['PetSupplies']=array('+pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A'); $sort_a['Photo']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A'); $sort_a['Restaurants']=array('relevance'=>'Featured items','titlerank'=>'Alphabetical: A to Z'); $sort_a['Software']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z'); $sort_a['SportingGoods']=array('relevancerank'=>'Best score','salesrank'=>'Bestselling','pricerank'=>'Price: low to high','inverseprice'=>'Price: high to low','launch-date'=>'Newest arrivals','sale-flag'=>'On sale'); $sort_a['Tools']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A'); $sort_a['Toys']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-age-min'=>'Age: high to low'); $sort_a['VHS']=array('relevancerank'=>'Best score','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-video-release-date'=>'Release date',); $sort_a['Video']=array('relevancerank'=>'Best score','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z','-video-release-date'=>'Release date',); $sort_a['VideoGames']=array('pmrank'=>'Featured items','salesrank'=>'Bestselling','price'=>'Price: low to high','-price'=>'Price: high to low','titlerank'=>'Alphabetical: A to Z'); $sort_a['Wireless']=array('daterank'=>'Publication date','pricerank'=>'Price: low to high','inverseprice'=>'Price: high to low','reviewrank'=>'Average review','salesrank'=>'Bestselling','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A'); $sort_a['WirelessAccessories']=array('psrank'=>'Best score','salesrank'=>'Bestselling','titlerank'=>'Alphabetical: A to Z','-titlerank'=>'Alphabetical: Z to A');

アメリカの人口は3億人弱で、日本の2倍以上の市場です。
チャレンジしてみる価値はあると思います。

しかし、外国のサイトのSEOって、どうやるんでしょうか？
リンク集とかあるのかな。