Amazon tends to be the slowest. Many who ordered 5D MK III's waited a month longer than Adorama, and B&H buyers waited longer yet.
All of this is Canon's doing, they hold back shipping large quantities if they do not like a vendor selling graymarket, for example.
Stores do not control the availability from the manufacturer.
I did not see you mention what product you ordered, a 1D X is going to be a bit of a wait. You will likely get it first from Adorama, or from a small local camera shop. Canon seems to help small shops out by sending them a camera or two on shorter notice.