I plugged USD100K into one of those "paycheck calculators" on the internet for California and after Federal, Social Security, Medicare, California tax and "CA SDI", I got S$81,506 (using 1.26 conversion) take home pay. That's S$6,792. Your paycheck in Singapore would only be S$4,875 as your CPF isn't disposable income i.e., its not in your paycheck. Social Security is similar to CPF and Medicare is similar to Medisave.

When all is said and done, you are S$1,917 poorer in Singapore. Furthermore, if you grew up in the US and are a US permanent resident, you are subject to US taxes anyway!