"Track" is a bit of an oversimplification: they also imprison US citizens who they suspect might be foreign, along with the actual foreigners, of course.

ICE releases teen US citizen wrongfully detained for over 3 weeks:

https://nypost.com/2019/07/24/ice-releases-us-citizen-18-wro...

ICE wrongly arrested over 1,000 US citizens in recent years:

https://thehill.com/latino/385261-ice-wrongly-arrested-over-...

U.S. Citizen Who Was Held By ICE For 3 Years Denied Compensation By Appeals Court:

https://www.npr.org/sections/thetwo-way/2017/08/01/540903038...

How ICE Works to Strip Citizenship from Naturalized Americans:

https://theintercept.com/2018/02/14/ice-denaturalization-nat...

U.S. Citizens Targeted by ICE: U.S. Citizens Targeted by Immigration and Customs Enforcement in Texas:

https://www.cato.org/publications/immigration-research-polic...

And that's not touching upon some of their more grievous ethical violations.

ICE is effectively a way for the executive branch to do away with due process.