I was out of town & missed ask that,, but I'd like to take a shot at clarify a could things for
@mumstheword . First, like I think someone else already said, most of the people involved in this mess aren't Mexican citizens. They are from an assortment of central American countries, fleeing an assortment of types of violence. (And I'm going to assume some of them might be bad people.)
The procedure for claiming asylum is to present yourself to authorities at the border and say that's why you are there. You then wait for an immigration judge to decide on your claim. There's a severe shortage of people working in that part of the system, and a long waiting list. There are a number of ways one can wait. In detention being one option. There are also assorted ways a person can be released, pending a legal decision. In the past, those were more often used. Naturally, some people failed to show back up in court. I think there's a lot of debate on how big that problem was. I have no reliable statistics, so I'm not going to go there.
Actually crossing the border undocumented IS a crime. But, like lots of things, it could be charged at different levels. In the past, it was more commonly charged at a lower level, which meant people were released, pending trial. Same situation as above. Some people show up in court, some don't, etc.
At the moment, it appears that locking people up is the preferred course of action. With more people detained, you have more overcrowded and the shortage of staff causes more of a problem.
It's true that someone jailed pending trial for any crime will be separated from their family. A major difference is their family will not also be detained. If there's no one to care for the children, they go into the foster care system. They are not held in mass facilities made from refurbished Wal-Mart stores. They are not held in an entirely different part of the country. There's a pretty good chance they can easily be reunited with their parents in due course.
This is being handled as it is because the powers that be have chosen to go this route. It's more or less within the law, but it's one of several options and it's more severe than options that were usually chosen in the past.
It's ridiculous for the president to blame this on the democrats. His party controls both parts of the legislature. They are the ones in power. The democrats can't change things, unless they choose to do whatever the republicans want them to do.