This doesn't justify it by any means, but the parallel between the Madagascar Plan and the issue with illegals in the US is actually quite similar in reasoning for how the perpetrators end up opening concentration camps.
There are several countries that refuse involuntary repatriation of their citizens. With the Jews in germany, same issue, hardly anywhere was willing to take them. And that's when you ended up with the perpetrator buffering them in these camps until they just gave up because there was no place to send them other than back into the broad population.
Of course it is the fault of the USA if these people are abused in these camps, but these peoples' home country are not doing any favors to the people stuck there by refusing to take them back.
People in i.e. France are dealing with similar issue where much of their criminals are Algerian because Algeria is refusing much of the repatriation of illegal immigrants in France. France has chosen to just release them back into population rather than build camps, with end result Algerian gangs terrorize the populace knowing they can't be sent back, which obviously plays into the hands of pushing voters towards the right-wing.
The German plan for deportation was never executed. There were programs against the Jews, they were persecuted and encouraged to leave, but the Nazis never formally banned them. They ended up going the other direction as genocide approached and made it impossible for Jews to leave.
But the situations are again nothing alike because in that case you're speaking of Germany trying to dump Germans on other countries. In this case you're speaking of the US returning e.g. Salvadorans to El Salvador, which the latter country generally having obligations under international law to accept their citizens. The handful of exceptions, like with Venezuela, have all generally been resolved.