Is there any realistic way to effectively defend against nukes?

Either have significantly more nukes or infiltrate the education system of your opponent and slowly teach each generation to be more and more anti-nuke until the country willingly abandons them.

Have nukes of your own.

Be Turkish
Nukes won't affect you.

Have a (You) for your excellent post and rare flag, my Rwandan brother

I'm not actually Rwandan I'm a Rhodesian Exile selling arms to Rwandans so they can kill each other

Israel, cheeky

They can be shot down. It won't be perfect, the bomber always gets through, but good interception systems and a robust civil defense system will ensure those outside the immediate blast zones will have a very good chance of seeing tomorrow.

In addition to this, a nuclear exchange will not be country versus country. Sure China could dump all of its nuclear weapons on the US and slow us down, except now they're all out of nukes and have to deal with the militaries of the rest of the Western world including nuclear capable UK and France. So take the number of nukes, remove a sizeble chunk that got blown up in the atmosphere, you'll probably have some fail due to technical issues, now take the remainder and divide it up among not only viable targets in the US but also those in most of western Europe.

DUM DUM
DIDDLE DUM DUM
DIDDLE DUM DUM

Highly effective for preventing casualties due to flying debris and roof collapse in the moderate and light damage blast zones.

You're doing God's work Strelok.