It honestly seems very unpredictable. Anecdotally the worst behaviour seems to have been at the most republican states but not exclusively.
For example the Australian who had a work visa and lived in the US for years flew in to Texas where it was arbitrarily nullified. There are plenty of stories of people crossing southern and northern borders and being detained by ICE. Thats included British, German, Australian and French cirizens that ive seen in the UK press coverage anyway.
As a US citizen you shouldnt have an issue but I'd probably travel through a major hub like JFK in New York to be safer. I wouldn't re-enter through Republican states like Florida, Texas, nor probably Washington DCs airports. Obviously travel on your US passport.
You should he OK as a US citizen but it does look like there is a breakdown in the rule of law in the US. People imagine that means riots and the police not able to keep control, but in this case its the government and government agencies doing whatever they want and the legal system unable to stop them.
I'm a UK citizen and am not intending to travel to the US - I often cone for a major conference but having seen what happened to the French scientist who had his phone searched and then was denied entry for criticising Trump I won't be risking it. I'm sure a lot of other UK and Europeans feel the same way.
Sadly the only 100% safe option for you is to not leave the country. Its madness as youre a US citizen but at this point things are still going through the courts and its not clear where this will stop.