You have to move the little black (or white) plastic screw retainers on the radiator support. Both sets of square holes are in the sheet metal stamping of the car. Look at your euro buckets and you will see the other hole pattern. You do not need to trim. To remove the plastic screw retainers pinch the part from the backside and pry it out the front with a small screwdriver. Then pop it in the other holes.
See the 2nd picture that shows the plastic screw retainers on the radiator support. You can see the I have them in the Euro setting.