Voting machines are vulnerable just like any other machine, and have been proven time and time again that they're not particularly difficult to hack. DEF CON has been doing it for almost ten years at this point. First time in 2017, with lots of articles covering it. The year after even TIME reported about how an 11 year old did it. In 2024 they got some attention again due to Trump going for second term. But I don't think much came of it...
The US is a flawed democracy, and has been on a steady decline for years.