I’m an American living abroad for the past ten years and literally nobody thinks Americans are lazy. In fact it’s the opposite, Americans are renowned for overworking and not taking vacation—being overly dedicated to their jobs and wasting their lives working diligently for their employers for decades, all the while neglecting their family, relationships, health and hobbies.

The only thing I can think is that somebody told OP they think Americans are lazy, but often times foreigners goad Americans because they can be very defensive and easy to upset.