Perhaps it's not as life altering as jail or fines, but still: no holidays in Florida or Hawaii. No meeting peers at a congres in the US. Not even using flights from American carriers to go to South America, as they will likely pass via a US hub.
Worse. If they ignore the whole thing, at some point they will get condemned of contempt of court. That's a criminal offense. That means you can try and get interpol involved. Once you have an interpol Red Notice to your name, international travel to any civilized country becomes complicated.