can I hard wire the output power of a eu solar inverter to a us breaker panel/
No you can't, because your neutral is floating, so any imbalance between L1 and L2 loads will cause imbalance between L1 and L2 voltage.
Perhaps it would work with a transformer tha has 230V input and center tapped 120V-0V-120V output, if you can get the grid tied inverter to turn on without a grid.