They are based in Singapore, they have a warehouse in the US. That doesn't make them a US based shop. There will always be a lag time between when you order and it getting shipped. 3dsgamerworld is the same way, they got a warehouse in the US. This isn't amazon prime, your not getting it shipped the next day with tracking within 2 hours of your order, nothing is automated when you buy a flashcart from any vendor.
Vendors that can ship from a warehouse in a country of a buyer, are known as virtual vendors. People that know what they are doing buy from these types of vendors for shipping times. Buying something from a chinese vendor site and getting shipped from china can take 2-4 weeks in shipping time depending on where in the world you live in. The UK, pretty much has only virtual vendors left due to the IP laws in place and how active customs is in seizing contraband.
There are less than 5 shops that are
physically operate in the US today compared to a few years ago. If you want to deal with US vendor, you can use modchipsdirect, they are one of the last US vendors.
http://www.modchipsdirect.com/
If your getting a 3DS flashcart like the Sky3DS+, even modchipsdirect can't ship it from the US. They have been using international DHL 3 day from asia, which roughly means your paying 30 bucks for shipping.