Trossard at the double as Arsenal beat Barcelona in Los Angeles
Belgian international Trossard netted in the 55th and 78th minutes as the English Premier League runners-up completed an emphatic victory at the SoFi Stadium in Inglewood.
The start of an entertaining encounter at the home of the NFL's Los Angeles Rams was delayed by 30 minutes after Arsenal's team bus was held up in traffic en route to the stadium.
When the game finally kicked off, Barcelona began the brighter, with Moroccan forward Abde Ezzalzouli producing a scintillating run down the left flank to set up the Catalans' opener.
Ezzalzouli's cross was met by Raphinha, whose first-time shot was saved by Arsenal goalkeeper Aaron Ramsdale, but only as far as Robert Lewandowski, who rammed in the finish in the seventh minute.
Arsenal however were swift to respond, with England international Bukayo Saka grabbing an equalizer in the 13th minute after a defensive lapse by Barcelona centre-half Andreas Christensen.
Saka missed the chance to fire Arsenal into the lead from the penalty spot on 22 minutes, the winger screwing his shot wide of the post after Ronald Araujo had handled in the area.
Barca however regained the lead just after the half-hour mark, with Raphinha's long-range free-kick deflecting off Martin Odegaard in the Arsenal wall to deceive Ramsdale.
Odegaard made amends just before half-time however, flicking on to Arsenal's new signing Kai Havertz, for the forward to jab in the finish from close range.
Arsenal dominated for long periods of the second half, with Saka missing a golden chance to put the Gunners ahead early in the second half, shooting over from five yards out with the goal begging.
Arsenal's pressure finally told though with Trossard scoring in the 55th and 78th minutes to make it 4-2.
Ferran Torres scored a late consolation for Barcelona in the 88th minute to give the Catalans a glimmer of hope, but Fabio Vieira made certain of victory with a long-range strike a minute before full-time.