Using a stand mixer with a paddle attachment, or hand mixer, cream the room temperature butter, brown sugar, and granulated sugar until smooth and creamy.
Add in the eggs and vanilla extract and beat until light, fluffy, and pale in color. This should take 2-4 minutes which seems like a long time, but you'll see a huge difference in the texture afterwards.
Add in the flour, baking soda, and salt and mix until thoroughly combined. The dough will be soft and slightly sticky.
Using a spoon or spatula, gently fold in the red, white, and blue sprinkles.
Cover the dough balls and chill in the fridge overnight for best results. If you absolutely can't wait, just chill it for at least 2 hours.
While the dough is chilling, preheat the oven to 350°F and line a baking sheet with parchment paper.
Place dough balls at least 2-3 inches apart on the baking sheet (they will spread, I usually only do 6 cookies on a half sheet pan). Place the rest of the cookie dough balls back in the fridge while the first batch cooks.
Bake at 350°F for 9-11 minute or until the edges are set and the centers are still soft. Remove from the oven and let rest on the baking sheet for 1-2 minutes, then transfer to a cooling rack.
If desired, immediately after removing from oven, garnish with extra sprinkles so they'll stick to the tops!
Notes
Store the baked 4th of July sugar cookies in an airtight container at room temperature for up to 4 days.