Can I go back to the United States with a ten-year visa for half a year and transfer to Spain?

Of course. According to the public security department of official website, the US 10 visa refers to the US tourist visa with the validity period of 10. Holders of this visa can enter and leave the United States several times within the validity period of the visa, and each stay lasts for six months, but the length of each entry is determined by US border control officials. If you plan to travel to Spain and re-enter the United States with a 10 visa, please ensure the validity of the visa and prepare sufficient materials to avoid trouble.