As with so many things, it takes a while for the law to catch up with the latest technological marvels. Chances are, you may have to go for an "entrepreneur" type visa - as, in effect, you are establishing a US "branch" of your company.

Your best bet might be to contact the US Consulate in Barcelona. (There may be a branch in the Canaries, but the branches often handle only certain types of transactions.) There are also immigration attorneys in Spain who can assist you (for a fee, of course - but it could be considered a business expense if you go with the "opening a US branch" plan).
Cheers,
Bev