A significant risk from even a small nuke is indeed the fire risk. It is likely that the fire department and municipal water sources will be overwhelmed.

The risk may be reduced a bit by reducing flammables near your home, and also inside the home near windows.
Prepare for a wildfire, even if you live in area not normally considered a fire risk.

Under normal circumstances, all but the very smallest of fires should be left to the fire department.
However an attack involving even a single small nuke, is not normal circumstances, and it is very unlikely that the fire department will be available.
As a minimum I would keep a few hundred gallons of readily available water, a few dozen buckets, and plenty of fire extinguishers.
Although often ridiculed, the old fashioned stirrup pump is astonishingly effective for such a cheap simple item. Every home should have at least a couple.
Better still would be a large water source such as a swimming pool, and an engine driven pump complete with suction and delivery hose.

Even if you consider such an event to be unlikely, fire prevention and fire fighting preps could be useful in the event of more conventional fires also.

If considering a new home, consider fire resistant construction.