If you never registered in your county, you're not registered.
There's a million different ways you can get on the mailing lists of both political parties. They buy or latch on to mailing lists from every source available.
The party campaign managers and chairmen know the lists are not fully accurate....but they don't care. They play the averages.
When I ran for office (successfully) years ago, I used a mailing list print-out of registered Republicans available from the county clerk.
After I mailed out my brochures, I received a nasty, whiney and sobby phone call from some babette who was all bent out of shape because the brochure she received was addressed to her dead husband, and it "brought back the grief". She tried to do a real number on me.
Of course she never had hubby's name expunged from the voters list, a simple-enough thing to do by calling the county clerk's office.
I'd betcha if she received a letter addressed to her deceased husband that there were some death benefits mistakenly denied his estate, she would have been jumping with joy. No "grief" there, LOL.
She obviously was an angst-ridden, Ophra-watching DemoRat.
The point I'm making is that don't get excited over something that is undoubtedly nothing. There's no hidden personal agenda directed just to you when you get mass-mailed political literature. You're just another pretty face.
You can always go to your county complex and anonymously check the voters rolls on their lists or computers if you feel the need. You DON'T have to give your name. It's public information.
The voters' names are listed alphabetically, and in most counties you can ask for the reverse....i.e., the list by addresses.
Best wishes to you.
Leni/MinuteGal
Florida