Router is no issue as it isn't connected to anything besides a cable modem. 2.4 channels are the same except there is one more (12-13?) at the high end over what is in the USA. 5 GHz should be the same. I'm assuming that your power supply is multi-voltage, which most electronics are these days.
Modem is a different issue. First, your provider may be supplying fiber, and second, IF the local providers will accept a customer modem on their network, it will have to be on an approved list and they'll need the MAC address to turn on the bits. And again, assuming that it is dual voltage.
Thanks for the comment.
I am well aware that SG is using different voltage and both are covered for 100-240VAC.
I am also aware of the fact that wifi channels for 2.4GHz go from 1-14 and US only uses upto 11. But this shouldn't be an issue unless I am in the middle of heavy wifi traffic and also I can always force my router to operate at a fixed channel.
I am more curious about the modem part. Fiber coax with DOCSIS 3.0 is the standard in US. But I wasn't able to find out whether Singapore is on the same protocol standard. For example, china is using EuroDOCSIS so using my modem is not possible for any local ISP. I saw some of the models from Linksys are being sold in Lazada website with the tag "Imported from US", so I assumed I can just unplug whatever I am using in US and take it out to Singapore... But I wanted to double check this before I decide to bring it. I wouldn't want to spend extra for those things... They are 2x more expensive in Singapore.