Usually courts are a lot more lenient with foreign citizens. Try to get jailed in Mexico as an French citizen - pretty hard unless you do obvious bad stuff.
From what I've seen, it's the opposite. Nobody wants an outsider coming into their territory and committing a crime. And it also makes you a flight risk, so that's going to factor badly into any pre-trial detention.
> Nobody wants an outsider coming into their territory and committing a crime.
Right but they don't want to deal with them either. They'll deport someone and ban them from entry (which can often be done essentially at will) rather than putting them through the whole legal process and potentially dealing with protests from their country of citizenship.
In fact, in Illinois there is a specific statute to cover this. The Dept of Corrections can simply dispose of someone's sentence and hand them to ICE for deportation. I knew a Mexican guy who had a 6 year term and I heard from him 6 weeks after he was sentenced -- he was back with his family in Mexico, having had his sentence terminated and quickly deported.
France can and will charge anyone on its territory no matter what passport you hold.