I will take a different angle from the other answers here. By saying you are 'not good at communicating' without elaborating on that, your boss might as well have said 'I do not like her' or more politely 'she is not a good culture fit'.
Communication is a two-way concept. If your 'lack of communication skills' here means not regularly providing enough information for them to be in the loop with what you are doing, that is something they could have addressed.
If it means it takes longer than average for the manager to understand something you are trying to convey or vice versa, again, it is something they could have addressed.
If it means you are not verbally active or assertive, which I take to be the case given your 'introverted' self-assessment and how you are emphasizing your inexperience, it is a culture fit issue when it comes to your communication style. You can either try to fit a 'louder' culture more or find a different organization that tolerates a more passive communication style. Neither way is intrinsically superior to the other but the American business culture seems to favor more active communication styles so one with such a style might have an easier time finding organizations that tolerate them.
At the same time there is a decent cost associated with changing your communication style: researching what that entails for you, changing your habits, mental cost of adjusting your habits, time cost of all the feedback and trial and error etc.
So in short, you can either find another org or place to work that has a communication culture that fits you in or change yourself to fit the org culture.