Then you can't have spent a lot of time in a big US city.
Illegal immigration in the US is not like Britain. It's not tens of thousands of people arriving per year and then being managed (or quite often mismanaged). There are likely approaching 15 million undocumented immigrants in the US, and by most estimates, ~80% have been here for more than a decade. They have built their lives here, they work, they are part of communities. But, there is no pathway for them to become citizens or at least legal residents. They have been trying to pass the Dream Act for about a quarter century to provide a pathway for at least the 2 million undocumented immigrants that came to the US as children to stay, but it's never gotten over the line (and despite Trump occasionally giving it lip service, his administration has focused on enforcement not rewriting the legal code).
That's why you might sometimes hear about sanctuary cities - these are US cities (and there's lots of them, including NY, LA and Chicago) that have decided to limit cooperation with ICE to protect undocumented immigrants from deportation. This practice started in the 1980s, and still goes on today.
What the Obama administration did was essentially twofold - deport recent arrivals as and when they are identified. And deport any undocumented immigrant that was convicted of a crime. As I mentioned earlier in the thread, this added up to about 3 million in his presidency, and in general, it was a sensible, pragmatic, humane policy. Some far leftists didn't like it, but most people were comfortable with it.
What the Trump administration has decided to do is send ICE into a series of major US cities, and arrest anyone and everyone they can find, regardless of how long they've been in the country, their age, family status, job, lack of criminal record etc. etc. And they're doing it without following the general principles of due process. They're also spending a ton of money on it (~$80 billion was allocated to increased ICE enforcement in the 'One Big, Beautiful Bill).
Which is a long way of saying that if you asked the vast majority of Democrats and a lot of centrists (probably quite a few traditional Republicans too.....but not the MAGA folks) in the US the question "someone is here illegally, should they be deported?", the answer you would get is "It depends".