He's got a well known habit for picking up injuries that relate to muscular imbalances. Either he lacks the muscular strength in his legs or doesn't recover properly after training. I'm think it is both given how frequent these injuries are. He has the talent to play at the top level, but not the body.
It's the very reason I've advocated in getting Sancho. I don't think Pulisic will ever be a player we can solely rely on given his injuries are very much self inflicting given the nature of his muscular system.