I am planning to buy a Nikon 55-200mm lens and I was checking prices at B&H and there is a $30 difference (almost 15% of cost) between "Imported" and "USA" lenses. What is the difference between the two? Is there any drawback of buying the "imported" lens?
It goes beyond warranty; Nikon USA will not work on gray market lenses AT ALL, regardless of warranty status and your willingness to pay. You have to find someone else to do it, or send it overseas to Nikon Japan (who won't honor the warranty but will at least take your money). Non-Nikon repair shops might be riskier due to parts availability and expertise issues (VR lenses are very complicated) and the fact that Nikon is pressuring (or wants to pressure) them into similar non-repair policies.
Thom Hogan has a more detailed article about it.
The biggest drawback is that Nikon and Canon USA do not provide warranty service for "grey" market goods.
B&H attempts to offset this by providing a "matching" warranty: BH matches up to one year of the original warranty, which ever is shorter.
Besides the OEM warranty, you also give up the cc warrant. Little known by many, in the US when you purchase an item with a credit card, the credit card company will double the manufacturer's warranty. This does not apply to imports. YMMV outside of the US (I guess it's one benefit for being a society that finances it's lifestyle with credit-card debt).
Also, albeit minor, you may not get an english version of the instruction manual. I purchased the canon remote flash transmitter and it ended up being the canon.jp model. The seller did have an English manual avail in PDF, but is was a bit of a nuisance.
They are the same lenses, but the difference is in the warranty offered. Nikon USA imports lenses and offers a USA warranty. Similarly, Nikon Canada does the same. They are different organizations. I live in Canada, so my experience may not be as relevant to you, but Nikon Canada will not service or offer warranty on lenses that were not purchased through an authorized Canadian dealer. On the other hand, Nikon Canada offers a 2 year warranty on cameras, and a 5 year warranty on lenses. For me, that makes it worth the difference in prices. (Similarly, Sigma Canada offers a 10 year warranty on lenses, compared to I think 4 years in the USA).
The term for merchandise imported and sold by a dealer not authorized by the local organization is "Grey Market". There's nothing wrong with the gear, it just may be harder to get it serviced and may have different warranty conditions.
There is also the possibility that some imported gear may be counterfeit or knock-offs of some kind, but I haven't run into that problem with camera gear yet.
Typically the imported lens might need to be returned to the country of origin for the warranty.
i.e. if it was imported from the UK (I know highly unlikely) and there was a fault you would need to send the lens back to the UK for repair - if you wanted to claim under the warranty.