is investment the main reason some countries produce low quality shows?

What are we defining as quality here? Global reach?

The only countries that produce shows with consistent global reach in the Anglosphere are the US and UK.

Nearly every other country produces shows in the local language for the local population.

If you're talking about production value then yes, more money would be the difference. But there are many high production value projects that ultimately end up being trash. The US generally has more capital flow to risk burning on such misadventures.

Yes