The congratulations came with a subtle message, however.
"The quality of our relationship will depend on the policies of the new government on a wide range of issues," said Jan Edmonson, spokesperson for the Bureau of Western Hemisphere Affairs, reading from a prepared statement.
"Obviously the MAS [Morales' party] doesn't want to provoke the U.S., but neither will it want to rely on the U.S.," said Jeff Vogt, senior fellow at the Washington Office on Latin America. He predicts Bolivia will likely strengthen its ties with Europe and its immediate neighbors.
"We are going to see tighter integration within Latin America," he said.
Experts believe that now that the campaign is over, Morales will cool his rhetoric and strike a middle ground between communism and economic liberalism, while focusing on strengthening Bolivia's weakened government. The nation has had five different presidents in the past four years.
"They will reassert the state as economic, political and social actor after decades of governments that weakened or dismantled state institutions," Vogt said, referring to Morales' party.
It has been called a pink tide instead of a red revolution.
"The new left in Latin America is not trying to emulate the Cuban model but rather strking a more pragmatic stance," Vogt said, pointing to the growing number of South American countries with left-leaning leaders like Brazil's Luiz Inácio Lula da Silva and Argentina's Nestor Kirchner.
"The left in 2006 in Latin America is far different than in 1976," said Julia Sweig, director of Latin American Studies at the Council on Foreign Relations.
Forget taking power through force and arms, the left now uses democratic channels. "It means, domestically, there's no rejection of markets, and it means independence and autonomy from the U.S. on the international scene," she said.
Bolivia has huge untapped natural gas reserves but needs money to extract the precious commodity. This will likely be Morales' first litmus test. He will have to attract foreign investors and also prove to his supporters that the cash infusion benefits his constituents.