The Cuban government denies accusations that it has troops in Venezuela.
The U.S. and more than 50 nations view Maduro's re-election last year as illegitimate because of fraud.
Rubio mocked reports that Maduro was defeating Guaidó three days after the opposition leader called for a military uprising on Tuesday that failed to push Venezuela's military into rebellion.
"This notion that Maduro is winning is ridiculous," he said. "This is a peaceful movement of civil disobedience."
Rubio said there are no questions there's a real threat to the U.S. Rubio said the U.S. government must be prepared to face Venezuela, and suggested the militant Hezbollah group is present in the South American nation. The leader of Lebanon's militant group has denied the claim.
"You look at all the bad players and see what happened there. You got Russia, you got Iran, you got Hezbollah. They are all there," Scott said. "To think that we are not going to have Syria in this hemisphere if we don't deal with this now. It's going to happen, it's just when it happens."
The lawmakers met with Romy Moreno, the wife of Guaidó's chief of staff Roberto Marrero. Marrero was jailed last month by Venezuelan authorities, who accuse him of being involved in a scheme to overthrow Maduro.
Also on Friday, the Trump administration ended a week of pointed but vague threats of a military response to the Venezuelan political crisis with a meeting at the Pentagon to consider its options, though there was still no sign any action was on the horizon.