HOUSTON – For three weeks, Jurgen Klinsmann has extolled the virtues of Copa America Centenario and, in the face of mounting skepticism, sold the promise of his U.S. national team.

Enthusiasm and good vibes — not to mention a resolute defense and a revitalized Clint Dempsey — have helped carry the Americans into the semifinals of the tournament. Now stands their most daunting hurdle, Lionel Messi and Argentina, tonight at NRG Stadium.

If ever there were a time for Klinsmann to temper his gusto and offer a more somber outlook, it's now.

No chance.

“There is no reason at all why we can't win Copa America,” he said. “Dream big. Why not?”

The Americans have already exceeded expectations. They surpassed minimum requirements by advancing out of group play and then sprang a minor surprise by defeating Ecuador in the quarterfinals Thursday in Seattle.

They've played hard, played together and played with emotion since losing to Colombia in the Group A opener. They've responded to adversity in critical stages — down a man for almost an entire half against Paraguay in the group finale and under intense pressure for the last 20 minutes against Ecuador.

Klinsmann has fueled the players' fire by playing the underdog card.

“With all the people who doubted us, [Klinsmann] brought the team together and blocked the negativity and kept it positive on the inside,” defender Geoff Cameron said. “Hopefully, we have another gear in us.”

They've answered questions about their capacity to win in the knockout round of a major competition after losing in the round of 16 in each of the past two World Cups. They've also rebounded from shortcomings in the Gold Cup and CONCACAF Cup last year.

And now they find themselves in position for an upset like few others in U.S. history.

“To play in the biggest games, to play in the toughest moments when everything is on the line, that's ultimately what we all want,” captain Michael Bradley said. “So a chance to play in the semifinals of Copa America on our home soil against a big team like Argentina, it's an incredible opportunity.”