Maybe you complain about the cold, but here in St. Petersburg where I live, it is colder. And still, everybody else in Russia lives some place even colder. To stay warm while cycling in winter, first never forget that in Syktyvkar, in Shchuchinsk, in Novosibirsk it is colder. Are you not lucky that it is only -15º C?
No matter where you are, wear lots of clothes. You don’t need special clothes, just lots of them. Wear underwear, long underwear, extra socks, shirts, sweaters, coats, overcoats, hats, scarves, mittens, gloves and more. It helps if they are made of wool and if you have something windproof on the outside. When it is -25º C, your nose hairs freeze as soon as you step outside, but the rest of your body is nice and warm, sealed up like a cosmonaut. Once you start pedaling, your woolen cocoon begins to heat up, everybody you know is literally freezing to death in the street like during the blockade, and you will be sweating.
Does it still snow in America? I hear that you have separate lanes for bicycles. How quaint! In Russia it snows a lot but does not get cleaned up very quickly. Snow becomes muddy and slushy and freezes at night. If your roads are clean, you do not need the studded tires I use in the winter, but you might consider replacing your 23cm racing slicks with as wide a tire as possible. Wider tires can be run at lower pressures, which will help you stay balanced on packed, uneven snow.
When the roads are covered in corrosive salts and chemicals, I leave my favorite bike at home and ride one that is already a piece of shit, a KhVZ Ukraina made in the USSR in the mid eighties from war surplus tank parts (tanks were made of bicycles during perestroika). It has 26” mountain bike wheels, really wide handlebars, big fenders, and nothing else. If you do not have room or time or whatever enough for another bike, no big deal. Just ride the one you already have. Learn how to lube your chain, consider getting some lithium grease and learning how to overhaul your bottom bracket and hubs. Sludge will rust your frame if your bike is made of steel and the paint is not 100%, so wipe it down periodically.