HI there, I'm Canadian and US buyers are used to way quicker shipping then we could ever provide. That means you'll get these emails from time to time.
here's my answer (after prompt shipping and a shipping notification without a tracking number):
Hi there,
So sorry you haven't received your package yet, they should arrive soon.
As outlined in my shop policies shipping to the US typically takes 2-4 weeks.
http://www.etsy.com/shop/cubits/policyAlthough its usually not that long, I cannot consider it late until after (4 weeks later). Could you let me know if the package has not arrived by then and I'll be happy to come up with a solution.