Service and warranty issues and EU SP dealers are probably forbidden from officially selling into the US market. If you add shipping and possibly custom duties, it probably doesn't make much difference at the end.
Do you mean that an authorised SP shop will refuse servicing or honouring the guarantee for their own products?
This does not happens here for products purchased directly in the USA (Apple, for example, or Dell).
When a product is sold with a "worldwide guarantee", it should be serviced all around the world, this is actually one of the best selling point for SP: their regs are supported by a worldwide network of shops, all carrying spare parts and which can fix you reg while you are travelling in exotic locations.
Other excellent brands cannot say the same, outside certain countries it is almost impossible to find shops capable of servicing them.
Regarding import duties, these are generally a very bad thing, and I warmly hope that all these additional taxations will disappear in this globalized world. Removing them within the EU market boosted the economies of EU countries, so I really hope that this unjust taxation for importing goods is removed worldwide.
In the meanwhile, however, there are ways to minimize these costs. I do not know the tricks for the route EU=>US, but I know a number of tricks (some fully legal, some not so much) for avoiding to pay high import duties when I purchase goods from US to Italy. A quick search on the Internet can show you some of these tricks. As said, some are fully legal!