Spanish and U.S. governments insist bilateral ties remain fundamentally solid, despite Spain's withdrawal from the Iraq coalition earlier this year.
Just more than six months ago, President George W. Bush counted Spain's conservative Prime Minister Jose Maria Aznar, among America's closest allies.
Mr. Aznar, along with British Prime Minister Tony Blair, was a key European supporter for the war in Iraq. The U.S. and Spanish leaders also shared strong Christian values, along with a determination to wage and win the battle against terrorism.
"I believe that prime minister Aznar was in a way probably closer to President Bush than say Prime Minister Tony Blair has ever been," said Charles Powell, a senior analyst at Elcano Royal Institute, a Madrid-based policy institute. "Partly because of these shared values - not only as Christian believers, but more broadly in their view of contemporary world history, of America's role in the world, and so on."
Today, U.S.-Spanish relations have fundamentally changed, in large part because Mr. Aznar is no longer in power. Three days after the March terrorist attacks in Madrid, Spanish voters handed Socialist opposition candidate, Jose Luis Rodriguez Zapatero, a surpassing victory in general elections.
Many blamed the Madrid bombings on Spain's involvement in the Iraq war, which the majority of Spaniards opposed, despite Mr. Aznar's backing.
Six months into his term, Prime Minister Zapatero has wasted no time putting his own stamp on Spanish politics. The 44-year-old leader pulled all of Spain's 1,300 troops from Iraq in a matter of weeks. He has shifted Spain's foreign policy priorities from building a strong alliance with the United States to renewing once-close relations with France and Germany and strengthening ties with North Africa and Latin America.
Antonio Remiro, a political scientist at the Autonomous University of Madrid, says in changing Spain's policy on Iraq Prime Minister Zapatero is simply fulfilling his campaign promises.
Mr. Remiro says Mr. Zapatero vowed as a presidential candidate to remove Spanish forces from Iraq, and he has done so. He is also making good campaign promises like fighting against domestic violence, and improving Spanish ties with countries like France. All of these initiatives, Mr. Remiro says, have been positive.
But Mr. Remiro faults the Zapatero government for, what he calls, its somewhat indelicate tone when it comes to dealing with Washington.
During a trip to Tunis last month, for example, the Spanish prime minister suggested that all foreign forces should leave Iraq - a remark that prompted U.S. demands for clarification.
The latest sign of frayed U.S.-Spanish relations occurred last week, when American Ambassador to Spain George Argyros decided to go hunting rather than attend a National Day parade in Madrid. Unlike in previous years, the parade did not include American troops.
The ambassador's absence sparked strong criticism from Spain's foreign and defense ministers. Mr. Argyros told the Spanish media that his decision was prompted by what he considered a slight during independence day celebrations last year, when Mr. Zapatero, then leader of Spain's main opposition party, refused to stand up as U.S. forces marched by with the American flag.
Despite the perceived slight, Ambassador Argyros, says relations between Spain and the United States are improving and will continue to get better. He told El Pais newspaper in a recent interview, "We are allies and friends."
Ordinary Spaniards, like 21-year-old Guadalupe Jordan, are far from displeased with their prime minister's performance - both at home and abroad. Polls show strong popular support for Mr. Zapatero's domestic initiatives, and high approval ratings overall.
Miss Jordan says she voted for Mr. Zapatero's Socialist Party in March because she did not like Mr. Aznar. She says Spain's new leader is doing a good job.
A recent poll taken by foreign newspapers found Spanish opinion of President Bush and of the United States in general ranked the lowest of the 10 countries surveyed. Only 13 percent of Spaniards said they approved of the U.S. leader, and less than half viewed the United States favorably.
In addition to opposing Washington's policy in Iraq, analyst Charles Powell says many Spaniards remain bitter about U.S. support for Spain's former dictator, General Francisco Franco who ruled the country with an iron hand between 1939 and 1975.
" So although there is a Bush factor, the anti-American feeling that can be attributed to current U.S. foreign policy has actually fed on an already strong base of latent anti-American feeling," said Mr. Powell. "And the result is that indeed, Spain is probably now the most anti-American country in Western Europe."
As an opposition candidate earlier this year, Mr. Zapatero endorsed Mr. Bush's Democratic opponent, John Kerry, in the November elections. But analyst Powell says Spain's government is being practical.
"I think it is clear to everyone the Spanish government would certainly prefer to deal with John Kerry in the White House as of next year and not with President Bush," he said. "Having said that, this government realizes that if George Bush wins, as seems most likely right now, they will have to do business with him."
Regardless of who wins the U.S. elections in November, Mr. Powell and other analysts believe Mr. Zapatero's government will try to improve relations between Madrid and Washington.