Leaving a trailer year round in the US.

It can be done! However, I wouldn't want to leave something stored outside during the summer months if at all possible. The hot Florida sun does a real number on RV's. I would want to find sheltered storage for the months when you won't be using it if you plan to be a snowbird i.e. staying in the unit for a good chunk of the winter and then heading back to Canada for the summer.

If you don't plan on traveling, consider looking for a "permanent" place in Florida. There are a lot of RVs that have been converted with the addition of permanent roofs, added sunrooms, updated aluminum walls, etc. Take some time to look at all your options.