This is complicated as it must distinguish between unauthorized status and unlawful presence; and more importantly whether you were maintaining J1 status per the DS-2019 when the change of status application was filed. If you were maintaining J1 status when the COS to B2 was filed, you were in a period of authorized stay until the denial of the COS application. Whether you are subject to the 3-year bar to entry to the U.S. based on 180 days or more of unlawful presence requires careful analysis of the facts. Please arrange for a legal consultation with an immigration attorney.
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The information provided in this answer does not create an attorney-client relationship and is not considered to be legal advice.
You should review your case with an immigration attorney. They will need to review the documentation to analyze the timeline of the events. Often there are waivers for past violations.
Please note that this response is for informational purposes only and does not create an attorney-client relationship.