It should be interpreted as an act of war that Mexico allows this.
This has SUDDENLY become a US problem because US Democrats have made it one.
The Democrats' purpose is obvious: to destroy President Trump and import as many pro-Democrat voters as possible.
It has SUDDENLY become a huge Democrat propaganda tool because Democrats and their henchmen are trying to nullify President Trump's heroic victory in denuclearizing the Korean Peninsula.
Hoards of Democrats and their henchmen, including lawyers, are at the Border developing ways of importing as many immigrants as possible for the purpose of packing the USA with pro-Democrat voters.
"Separation of Families" has become a propaganda tool for them.
There is no reason why families should be separated: Allow NO ONE to immigrate into the USA. Children remain with their parents. Those who come to the US-Mexico Border without their parents are not admitted to the USA and remain under Mexican jurisdiction and protection.
Republicans, such as Paul Ryan, who co-operate in this ignominious propaganda campaign, are stooges of the Democrats.