This year a tiny timing can lead to dramatic differences in realized trades. I experience the same thing live recently with daily rebalance. A lot of breakout trades fail recently and in this earnings season a lot of AIFactor favorites crash hard post earnings. From the shape I suspect this is a microcap system?
Check and compare the realized trades. Sims use Saturday ranks and the start date defines the trade day for weekly rebalance. Live strats use actual daily ranks, so ranks get updated the day after earnings for the ticker, NOT like in the simulation on saturdays. The only truly comparable sim/live setup would be weekly on mondays for both.
Usually live performance can be even a bit better than expected since you get the new rank info daily not weekly and you always trade on freah info. I don’t know what’s going on this year but many US strategies seem to fail hard recently. It looks like a bit more stocks, a bit looser rank tolerance, a bit more conservative universe and your US return is not 0% but suddenly 30% YTD.