I couldn't find any rule regarding sliding into second base in the USSSA rule book. There's a rule about intentionally interfering with a fielder making a play on a ball. The rule below seems to only refer to fielding a batted ball rather than the turn of a double play, but could potentially be applied to that situation. In real time, it was probably impossible to tell. It also didn't seem to make a big impact on the ability to make the play, so I say no interference. Slide was basically directly into the bag with arms a bit extended. Good hard play, imo.

"B. When the base runner interferes with a fielder attempting to field a batted ball
or intentionally interferes with a fielder catching a ball or throwing a ball, or with a
thrown ball.
EFFECT Sec. 5. B. If the interference is not ruled intentional; the batter-runner is entitled
to go to first base. If, in the opinion of the umpire, the interference is an obvious attempt to
prevent a double play, the immediate succeeding runner shall also be called out. When a base
runner interferes after he is out or after scoring, the most advanced runner shall be declared
out. "