It's possible that the United States never landed on the moon, but I would put that possibility at less than 0.000001 percent. There's plenty of evidence that the astronauts actually did land on the moon. There's no way to prove it 100 percent, so there will always be conspiracy theories, but it's very, very likely that the United States did land on the moon.
The evidence is overwhelming that the USA did, in fact, land on the moon. If the evidence was falsified, the number of people who would need to be involved in the conspiracy makes it extremely likely that someone would eventually leak the truth, either for money or their conscience. The government employees involved in the deception would also have far more to lose than to gain, so it is extremely unlikely that any evidence has been faked.
No, there is no chance the US never landed on the moon. We have proof of the moon landing; video and photographic evidence. However, if you do not trust this evidence, then you must consider something else. If the landing were a hoax, you have to imagine all the thousands of government employees who would have to keep quiet. If it were a hoax, at least one person would have leaked it to the press, if not for money then for fame.
No, it would be impossible to hide such a big secret for so long. The Soviets wouldn't waste the chance to spoil the USA's victory in the race to the Moon, but they actually congratulated NASA on the achievement. Given that there were so many people involved in the whole operation, the KGB would easily find someone who knows something about the "conspiracy".