The Tartan Army face an anxious wait to see if they qualify for the knockout stages as one of the best third-placed finishers after being beaten in their final Group C clash in Miami on Wednesday (24.06.26) and the coach acknowledged that the result could prove terminal for their hopes of progression.
Clarke told BBC Sport: "We made it difficult for ourselves. That's it. We gave them the goals and gave them the game they wanted. Disappointed. I think we're going home."
He added: "We created some chances, but didn't take them. Let's be honest, the best team won.
"The shift that the players put in, the ones that played 90 minutes in that heat, that humidity, were outstanding. But we have to be better. If we want to compete at this level, we have to be better.
"In the first five minutes, we're moving the ball quite nicely on the pitch. I thought we were settling into the game alright, and then we make a mistake like that [for Vinicius Junior's opener]. You cannot do that at this level, because it puts you on the back foot, and then it becomes a long night.
"Only Scotland can get a winnable first game, and then get number five in the world, and number six in the world with the next two games. That's the level we're at."
Scotland captain Andy Robertson also struck a downbeat tone and lamented the defensive mistakes that were ruthlessly punished by the five-time winners.
The full-back said: "Time will tell. We need to take a day or two to see what has happened. As a collective, we didn't want to put ourselves in a position to hope for favours. If you ask me now, I don't think it is enough. The next couple of days will be horrible.
"In certain moments, we let ourselves down tonight. At times, we were comfortable on the ball and got ourselves into dangerous areas. But against these teams, we cannot afford to make the mistakes we were making.
"We were punished for pretty much every mistake. It's not good enough when you get beaten 3-0. We only have ourselves to blame."