Serious questions about the "millions of us already had/recovered from this" theory

My girlfriend's daughter is a nurse in Baldwin County, AL and is convinced that Covid-19 has been with us since at least last December. She said that they have seen and know of countless people in the Mobile/Baldwin area that had flu like symptoms with unusually dry unproductive heavy smoker type coughs that lasted for many days after they recovered and the vast majority of these cases tested negative for the flu. She said that they had a handful of hospitalizations back then with people complaining of these weird "flu like" symptoms but from people testing negative for the flu and the doctors describing it as "a new strain of virus going around this season"

I (mid 40s) had what I thought was the flu back in early December and again in early February that at the very beginning started with the typical raw sore throat that quickly subsided. It then had a fever, was very tired, had a bloated "tight" feeling in both lower and upper chest with mild chest tightness, minor to mild shortness of breathe, minor aches, some sneezing, very forceful and relentless dry cough to the point of throwing up on occasion but with nothing to throw up, some nasal drainage, but I never got to the point I usually do with the many colds I've had in the past where I would typically start hocking up big loogies at some point. Had these symptoms both times. Had a short episode once during both "colds" where I woke up with my heart racing for a couple of minutes before subsiding. I even had some mild wheezing which I've never experienced previously during the last time in early February. The most unusual symptom both in early December and again in early February was that after the 4 or 5 days of flu like symptoms were gone and I felt much better and went back to work I still had a annoying dry cough with no other symptoms that persisted from early December all the way until mid February about 2 weeks after my second "cold" ended in early February.

There were at least a handful of people where my girlfriend's daughter works that were going to the hospital as a precaution due to the forceful dry unproductive cough and occasional asthma like shortness of breathe even back in December and January. Because there was no Covid test at the time and these people were all testing negative for the flu almost all the people coming in were given steroid shots and a Z-pack and told to rest and recover at home which they did.

What is the medical world's opinion on the thousands and more likely millions of Americans who had these unusual symptoms I had dating back to December and even early February with regards to coronavirus? Is it possible all the people back in Dec and Jan who had these symptoms couldn't have been from Covid or do the experts know for sure it's only been in the U.S. since mid January at the absolute earliest?