Nobody thinks it could happen while the US congress is dominated by Republicans, Trump is the president, and the Supreme Court is 6-3 GOP.
But, if the Democrats win big enough in the 2026 midterm elections to overcome all the dirty tricks that the Nazis are going to use to try to stay in power, then maybe in 2027 there's a chance they could start holding Trump to account. But, Trump would still have executive authority and unless he were impeached and this time they actually had the votes to remove him from office, they still couldn't get his Justice Department to investigate his War Department. Even if they did impeach him and remove him from office, he's just be replaced by Vance who is part of this whole signal chat.
So, at a minimum it would probably be 2029 before anything could happen, and would require that the Democrats got a congressional majority in 2026, and held or improved it in 2028 while also taking the presidency. And even then, the Supreme Court would still be 9-3 GOP unless some of the GOP members quit or died. So, it would probably require something radical like expanding the court to get any attempted convictions of higher-up GOP members past that court.
And, that's even assuming that the democrats grew a backbone. If they did, they couldn't do anything to Trump because the Supreme Court already decided the president is immune from anything up to, and including ordering Delta Force to kill the Democratic presidential hopeful. They could maybe go after Hegseth and down, but realistically would they? How many times have the Democrats had a chance to nail Trump, and instead decided that in the interest of national unity to let his crimes slide.
Then there's the International Criminal Court. They might risk indicting Hegseth or even Trump for war crimes. However, the US passed the Hague Invasion Act, effectively saying that if any American were ever put on trial for war crimes, the US would invade The Hague. That might deter them from even trying. Under Trump, they've already made life hell for a prosecutor who was going after someone who was merely a US ally. If a Democratic president were in office and a Democratic congress were in charge, they probably wouldn't actually invade, but they still might just ignore any ICC ruling. The US has made it abundantly clear that they're the world's only superpower and that international law doesn't actually apply to the US. And if anybody disagrees, they're welcome to take on the US military.