They aren't illegal if they are requesting asylum, which most are.

Russia and China? There was a surge of Russian asylum-seekers after Putin invaded Ukraine. They were afraid they were going to get drafted. In fact, I think some of them had been but ran instead. So, yeah...I would have expected a lot of Russians over the past couple of years.

And do you have to ask about the Chinese? Their society is horrible about human rights. So I'm sure many try to request asylum. Whether it's granted in a different question. Most asylum-seekers either don't pass the initial interview, and don't win in court.

The wall was a stupid idea. In most places along the border you can't actually build the wall on the border. For example, the Rio Grande (can't build it in the middle of a river). And if you build it on our side, then the asylum-seekers are in US territory if they get to the wall, and have the legal right to request asylum. So it's utterly pointless.

You have to change the law, which the Lankford group was trying to do, but Trump shot that down before anyone knew any details. It's questionable whether the restrictions that have since come out would have been in accord with treaties about refugees, as albaby explained in detail. But it's moot since the law isn't going to change, and so an unlimited number of asylum seekers will have to be processed. There is no legal way to stop them.