PREP: Preheat the oven to 350 degrees F. Lightly grease a 9x13-inch pan with nonstick cooking spray. Add pretzels to a large plastic bag. Seal without air in it and crush pretzels using a rolling pin. Crush to coarse crumbs; we don't want the crumbs too fine. Measure to be sure you have 2 full cups (160g) of pretzel crumbs. Melt butter then set aside to cool to room temperature (don't add hot butter; it will make the crust greasy).
PRETZEL CRUST: In a large bowl, mix together the crushed pretzels, melted butter, and sugar until combined. Press this mixture firmly into the bottom of the prepared pan (no need to go up the sides, just the base). Use the bottom of a flat 1-cup measuring cup to press down crumbs into a firm crust. Bake for 8-10 minutes. Remove and let fully cool before adding the filling.
FILLING: Meanwhile, beat the softened cream cheese in a large bowl until light and fluffy, about 1-2 minutes. Add in the sugar and vanilla extract and beat until combined, 1 more minute. Use a spatula to gently fold in the completely thawed whipped topping into the mixture until no streaks remain.
FILLING CONTINUED: Spread this mixture onto the completely cooled pretzel crust. Smooth it evenly so that none of the crust is exposed (otherwise the Jell-O will seep through). Take your time to really seal the edges here with the filling. Chill for one hour.
JELL-O TOPPING: Bring 2 cups of water to a boil. Add the gelatin to a large bowl and pour the boiling water on top. Mix well. Chill in the fridge for 10 minutes. Meanwhile, thinly slice the strawberries. Remove the gelatin from the fridge and gently stir in strawberries. Make sure the gelatin mixture is at room temperature, not hot. If it is still hot, chill for another 5-10 minutes. Hot Jell-O is going to break up the cream cheese layer! Once at room temperature, use a slotted spoon to gently transfer strawberries atop the cream cheese layer in an even layer. Then gently pour the gelatin over the strawberries in one even layer.
CHILL: Cover the pan tightly and refrigerate until completely set, about 2-4 hours. Once fully chilled, use a very sharp and hot knife (run under hot water then dry) to make cuts. The first couple of bars don't come out super well, but after that, it gets a lot easier! Be sure to cut all the way through the pretzel crust before removing bars.
STORAGE: These bars are best within 1-2 days of making. After that the bars begin to get watery/seep out liquid. These bars do not freeze and thaw well.