Should my online IT startup be considered an exporter?

Question

Our query considers an IT startup offering online services, with its servers being located in the USA and its clientele mainly in the States for the time being but eyeing up a further international sprawl in the years to come. As our nationalities and locations are wide spread (we are a UK-based Greek, an American (US based) and a Canadian (Alberta based), we have concluded that the most suitable form of incorporation that suits our case is perhaps a UK-based LLP, but any further suggestions or advices on topic are more than welcome. First thing I want to ask is whether this will be considered an “export” of a service and secondly since our income will accrue from US customers, if we will be liable to the American tax law (with all the entailing administrative work). I would really appreciate any guidelines on this rather complex issue.