Preheat your oven to 350°F (175°C). In a mixing bowl, combine crushed pretzels, melted butter, and sugar until they form a sandy mixture. Press this mixture firmly into the bottom of an ungreased 13x9-inch baking dish, ensuring even coverage. Bake for 10 minutes until lightly golden, then remove from the oven and allow it to cool completely.

Once the pretzel crust has cooled, beat together the whipped topping, softened cream cheese, and granulated sugar in a large bowl until the mixture is smooth and well-combined. Spread the cream layer evenly over the cooled pretzel crust and refrigerate for at least 30 minutes.

In a separate bowl, dissolve the strawberry gelatin in 2 cups of boiling water, stirring until fully dissolved. Allow this mixture to cool, then stir in the thawed sweetened sliced strawberries. Chill until partially set, about 30 minutes.

Spoon the Jell-O topping over the chilled cream layer and spread it evenly. Return the dish to the refrigerator and chill for at least 4-6 hours until firm.

Cut into squares and serve with additional whipped topping and crushed pretzels if desired.