Your “whites are now physically and psychologically unable to defend themselves” would seem to be contradicted by the enormous number of guns purchased by whites.
Don't forget the prodigious amount of ammunition also purchased by said whites.
Urban Feral foragers will find themselves being hunted by those who “surround them”.
Rule One in Race Wars 101:
1. Make absolutely sure you are in the majority in any race war you participate in.
A lot of gun buying is a fantasy by the purchasers. There is no effectively organized resistance. Each gun buyer will find himself an isolated little atom without support easily destroyed. Years of highly intelligent propaganda eternally repeated has destroyed white will to resist. It is possible effective resistance could come into being, but not probable.