Answer:
I'm not 100% sure on this, but I'll tell you what I think this is trying to say.
I believe it's criticizing the US-Mexico border and immigrants coming in with "open", or no, restrictions, represented by the open door.
I also think that the artist is trying to portray the immigrants as people that they don't want in the country and as a ticking time bomb.
I'm not 100% sure, but that's what I think this cartoon is trying to portray.
