Speaking as a US buyer, I have no problem at all purchasing from shops outside the US. I've ordered from Canada, Thailand, the Netherlands, UK and Australia...never had an issue with customs. Most packages have been small in size and value so that may be part of the reason they haven't been held up in customs.
I am aware that it may take longer due to customs etc. so if it's for a gift or for a specific deadline I keep that in mind when I order.