I see from qrz.com and the ARRL database that you have a General Class Licence. Under CEPT 61-01 only Anvanced or Extra class US licence holders can take advantage of the reciprocal arrangements under the CEPT 61-01 arrangement.
However. under the ECC REC0506 regulation US General Class licencees may operate as equivalent to the CEPT Novice licence in countries who are part of the ECC Rec0506 arrangement. This means you may operate on the bands, modes and powers that the EU - CEPT Novice licence holders can.
(all US states are listed, I simply shortened this graphic)
THERE IS A PROBLEM HERE however as Spain has NOT signed up to the ECC REC0506 arrangement, only the CEPT 6101 arrangement.
In short you can only operate in the countries in the table below but not Spain (you could operate in Portugal for example but not Spain):
ANNEX 2: TABLE OF EQUIVALENCE BETWEEN CEPT NOVICE LICENCE AND NATIONAL NOVICE
LICENCES OF CEPT COUNTRIES
Note the US NOVICE class IS NOT the same as the CEPT NOVICE class - the CEPT NOVICE is a step higher.
Please check out the full documents for any updates (Spain may sign up in the interim) and if you want more information - do a web search on CEPT Recommendation T/R 61-01 and ECC Recommendation (05)06.
You can also apply directly to the Spanish Authorities for a temporary licence under the old arrangements (i.e. not through the simplified CEPT / ECC system) - perhaps some Spanish SOTAist can provide the contact details?