50% of the world lives in Valeriepieris circle and a LARGE section of that are islands like Japan and the Phillipenes. The world will go on just fine.
The way I look at this movie is we are only seeing a VERY small section of what is going on in one tiny corner of the world. The JSDF can't send a rescure team for one Idaho farmer and his family.
I mean... lets be honest, how many of these creatures can there be any where. You tell me an APC with a 50 cal can kill them. A tank. Jets? We see a little girl with a pipe kill them.
There are so many holes in the plot we have to try and enjoy it without thinking too much about it. Lets face it, the lore is weak.