As said by others in the comments, there are quite a few things that come into play here, which all would be true regardless of who the actual sitting President is.
- The Constitution of the US is seen as the Supreme Law of the Land. The US being subservient to the ICC would be a direct violation of that. The ICC does not and cannot carry any legal weight in this country.
- There are already laws in place saying that the US can and will use military force in order to extract a US citizen held by the ICC.
- The US is, by far, the most powerful military in the world, and it isn't even close.
- The US is also the cornerstone of the global economy. Any attempt at enforcing sanctions against the US in order to force compliance with any kind of international law would likely simply be ignored, and would probably do more damage to the sanctioning country than to the US anyway.
- The US is host to the United Nations. I don't think I have to say what kind of shitshow would happen if the UN tried to arrest the leader of the country that's hosting it.
The ICC could issue a warrant for Trump's arrest as a symbolic gesture, but it would have about as much practical effect as if I had issued it.
It would have accomplished exactly nothing if they did. Voters aren't interested in "fixing the system". It would have come off as Democrats caring about nothing but "making power grabs" while ignoring kitchen table concerns such as the price of groceries. It would have come off as Democrats being more disconnected from the needs of everyday voters than they already are.
Harris, or whoever the dem nominiee would have been, would have been focusing on "fixing the system" while Trump just made all the same empty promises about "bringing down the price of eggs on day one", and he would have won by an even wider margin. Your average voter gives exactly zero shits about how things work in DC and what does and doesn't need to be fixed.