What you are saying doesn't make any sense. So you think that ICE will randomly arrest anyone in the street or around the stadium when they know that the world cup is going on and fans of different countries will be in their country to support their national teams. If you go to the US legally for the world cup why will you be detained? There's definitely going to be documents that will indicate that you came to the country for the world cup. Everything you said here are all lies. The US will be safe for the world cup and their traveling fans. Saying that ICE don't care if you are there to watch football or not is a false information you are spreading, and it's not healthy for the community.
I am pretty sure they will be ordered to stand down during that period without a doubt. Don't get me wrong, we all know (the whole world) that ICE agents have a great fun at locking people up, they have done so to people who are not just US citizens that became citizens later on, like someone who was born in Mexico but went to USA and became a citizen, no no, they actually arrested bunch of US citizens that were literally just Americans, literally like they were born in USA, their parents did, their grandparents did, not some person who became American later on, they love just locking anyone up, that's their fun.
These are the "cops" who murder or blind people because they just like to. So yeah, if the orders were to continue, then they would lock anyone they see during the world cup too. But they will 100% be told to stand down and not arrest anyone during that period, and they will avoid making a scene, so that USA could save face a bit. Sort of like Berlin Olympics during Nazi period.