The answer is Portugal!
Iceland does not border Spain. Portugal and France do though.
Portugal.
Andorra is its own separate nation. It borders Spain and France.
Spain
The European countries that share a border with only one other nation are Portugal, which borders Spain, and Denmark, which borders Germany. Additionally, Monaco borders only France, and San Marino is also bordered solely by Italy. Lastly, the Vatican City is an enclave surrounded entirely by Rome, Italy.
Andorra is its own separate nation. It borders Spain and France.
Spain is the only country which Portugal borders. In addition to Portugal, Spain also borders France, Andorra, the United Kingdom and Morocco.
France connects Spain to the rest of Europe, however, Portugal does not border France as it only borders Spain.
Spain
The nation of Spain is a nation whose name begins with an S and is south of France.
Kampala is the capital and largest city of Uganda, the only landlocked nation that borders Lake Victoria.