You will need to get a Malaysian licence issued, based on a validation of your US ATPL - no big deal, if you have the required experience. You'll do an Air Law exam, and a medical, pay your money, and Bob's your uncle.
"
Singapore and Malaysia they always state that you must be a citizen" - sorry, not true. There are hundreds of expats flying for SQ, and MAS still have a significant number I believe.
...but it doesn;t seem fair
Did anyone ever say it was supposed to be?