Over time their economies will dwarf that of your own and a larger economy means a stronger military.

Most white dissidents that advocate for traditional societies don't want the entire white race living in the sticks while the rest of the world advances to supreme military systems. That would be stupid and suicidal. If the Hutterites, Mennonites and Amish can live within the jew controlled clown world they can certainly live within a national socialist imperium as well. In fact I think a strong white fascist state would be even more robust with a healthy Amish like community inside it's borders.

Also how strong would non white countries really be if the bulk of white people turned inward and focused simply on living simple non technological lives? I doubt that most non white civilizations would really grow that rapidly without white inventions, white manufacturing advisors, and white consumers to sell too.