You need to start with basic anatomy and proportions. Study real human figures and apply that knowledge to your comic characters. Also, learn about different shading and inking techniques to add depth and texture.
First off, familiarize yourself with the typical styles and tropes of American comics. Then, practice a lot - do sketches every day. And don't forget to study perspective and composition to make your drawings more dynamic and engaging.
To draw American comic art well, you have to understand the use of bold lines and vibrant colors. Also, observe how famous comic artists handle action scenes and facial expressions. Keep practicing and evolving your style over time.