abolishing ICE would improve city air quality tho

lt would increase car traffic, so quite certainly no.

In Germany, Netherlands, and Switzerland ICE is the "InterCity Express" that links cities across the three countries.

In some countries it is. Everywhere else refers to internal combustion engines, which also would complicate getting around if abolished. On the other hand, nobody is proposing a ban on outboard motors for cars so there might be a market for those, I suppose.

Do you like think ICE is public transportation or something?

Sure, Intercity Express.

But apprently we are talking about US inmigration politics instead, as l got from another comment already...

ICE disambiguation in descending order of relevance:

• Internal Combustion Engine, the normal kind of engine in cars and heavy machinery
• In Case of Emergency, privileged phonebook entry to be contacted if you're in the ICU
• InterCity Express, European high-speed rail service
• Immigration and Customs Enforcement, the United States version of the SA
• Immigration Compliance Enforcement, the UK version of Frontex

Is ICE a transit agency somewhere?

A type of train connection, the ICE-(Intercity-Express)-Network.