did u do it step by step bro?
i had to try few times b4 i got it right .. always make backup just in case

1) go to main Diablo3 folder (C:\Program Files (x86)\Diablo III\)
2) look for these 2 files; .agent & Launcher (both are .db files) .. make backup b4 editing
3) open both using Notepad and edit/replace all "enSG" to "enUS" (using the find function)
4) Now if u start launcher it should start updating BUT if u see 2+ GB download .. theres another step to do
5) Go to folder C:\Program Files (x86)\Diablo III\Data_D3\PC\MPQs
6) Look for 3 files enSG_Audio.mpq, enSG_Cutscene.mpq & enSG_Text.mpq (make backup 1st) .. rename all 3 to enUS_Audio.mpq, enUS_Cutscene.mpq & enUS_Text.mpq (IF enUS_Audio.mpq, enUS_Cutscene.mpq & enUS_Text.mpq already exist in that folder ... move them to your backup folder then rename the SG ones to US)
7) Start launcher and u shud see few mb update in progress

Good Luck

p/s: btw im alrdy updated and in the game now after following those steps above

Same...  I tried SG > US trick...  Can play US server only, not asia