Preheat your oven to 350°F (175°C) and grease a donut pan.

In a large mixing bowl, whisk together the flour, granulated sugar, baking powder, and salt.

In another bowl, combine the milk, melted butter, eggs, and vanilla extract. Mix until well combined.

Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix.

Divide the batter into three bowls. Leave one bowl plain, add red food coloring to the second bowl until you reach your desired shade, and add blue food coloring to the third bowl.

Using a piping bag or a zip-top bag with the corner snipped off, fill the donut pan with the different colored batters in a striped pattern to create a flag effect.

Bake for 10-12 minutes, or until a toothpick inserted into the center comes out clean. Allow the donuts to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.

In a small bowl, mix the powdered sugar with 2 tablespoons of milk to create a glaze. Dip the cooled donuts into the glaze.

Decorate the donuts with sliced strawberries and blueberries to resemble the American flag.