Lucky you. I've found myself queuing for 15-20 minutes at Changi (especially T1 and T2), though it is true that at other times the wait has been minimal. Adding American visitors (especially arriving on USA-originating flights) certainly won't shorten the queues.

Bottom line: if this doesn't give Singaporeans access to GE kiosks at US ports of entry, it's a mystery why Singapore would agree to it. Given our political climate right now, any decision which helps foreigners and hurts SG locals would be an odd choice.