Do you use Phrasal verbs when you try to speak American English? Do you know a lot of them? Are you comfortable using them? Do you understand and know what a lot of them mean? What about prepositions? What about vocabulary? Have you ever had someone from the United States teach you American English phrasal verbs, prepositions and or vocabulary? If you're wanting to speak better in American English then knowing, using and being able to say Phrasal verbs, prepositions and having a good general knowledge of basic/intermediate vocabulary is VERY important. That way you're not repetitive with what you say or feel the opposite.. 'limited'. What does 'Fluent' mean to you? Are you wanting to be able to say things the right way the first time you say it...and not make mistakes or have your listener have trouble understanding you. Do you want to speak 'Okay' in American English...or really be able to speak the language well and comfortably and confidently so your listener doesn't have to 'assume' or 'figure out' what you're actually trying to say.