The six-member delegation of congressional Democrats, led by Senator Patrick Leahy, met with Foreign Minister Bruno Rodriguez as well as officials in agriculture, technology and the arts.
The four senators and two US representatives also visited dissidents and Roman Catholic leaders.
Their two-day visit came ahead of talks on Wednesday and Thursday between Cuban authorities and the highest-ranking US official to visit the communist island since the 1980s.
Roberta Jacobson, the US assistant secretary of state for Western Hemisphere affairs, will head the American team during two days of negotiations on immigration and the reopening of embassies.
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"Finally this president(Barack Obama) came to the realisation that that policy wasn't serving the best interests of the United States, of Cuba, or of the world," he added.
"Now we are moving toward a new era," he said, five weeks after Obama and Cuba President Raul Castro announced their intention to normalise relations.
The lawmakers said their visit was aimed at discussing how the two nations, which have not had full diplomatic ties since the 1960s, can cooperate in the future.
"We don't want anyone to have to worry about whether or not there will be potatoes on the shelves, or milk on the shelves, or pork or beef or grains or fruits or vegetables," she said.
"We would love to be in partners in that as well."
But some lawmakers have criticised Obama's decision, with Republican Senator Marco Rubio, a Cuban-American, saying the White House had "conceded everything and gained little" from the Castro regime.
But the US Congress still has the final word on ending the five-decade-old embargo that has forbidden most commerce and general tourism, a key industry for the country of 11 million.