Nukes are very expensive and dangerous to make, but yes all countries I am sure have the people and materials, and possibly the money to make a nuke if they wanted to.

But in a nutshell why they don’t. 190 countries back in 1970, including the US, Russia, UK, France and China have joined the Non-Proliferation Treaty (NPT). India, Israel and Pakistan never signed the agreement and North Korea left in 2003. The NPT recognises five states having nuclear weapons - US, Russia, France, UK and China - all of which had tested nuclear weapons before the agreement came into effect.

Under the agreement, these countries should not maintain an arsenal forever. And both the US and Russia have significantly reduced their stock pile.

The treaty prohibits non-recognised states from developing nuclear weapons. South Africa, and former Soviet Union countries Belarus, Kazakhstan and Ukraine have all given up theirs.

So with Iran actively trying to build a Nuclear bomb they are in direct violation of this treaty.

https://m.youtube.com/watch?v=0jfv-uvwF14

https://www.bbc.com/news/world-42873633