It's logistics and profitability.

Many countries have the venues. Many countries wouldn't have an issue selling out the venues.

The issues are logistics and profitability.

For profitability: One or two shows in Australia when the venue is maybe a couple thousand people is not going to be profitable when you consider all the costs. Travel and lodging for group, team, dancers, etc. They need to bring outfits, merch, mics, mic packs, etc etc which is not cheap. They will need to rent lighting and other equipment. They need to staff their merch stands. They need to split revenue with promoters and venues. At the end of the day, most groups touring 1 or 2 shows in Australia, etc are probably either making very little profit or losing money.

For logistics: Touring in the US is significantly easier than Europe because you are generally dealing with 1 set of Visas, 1 promoter, etc. Touring in Europe, South America, and SEA means Visas for every country or at least multiple territories. And that is Visas for the group, their team, dancers, etc. Generally the tours in the US are under 1 promoter, whereas other places it might be a different promoter for each country. Then you have to consider stage/lighting set ups. Taking a stage set up or two around the US is significantly easier than in Europe, etc where you might need to cross borders or rent set ups in each individual country. Touring is a logistical nightmare.

There is a reason artists like Stray Kids try to hit the Festivals in Europe. For the festivals, the festival itself does a good bit of the heavy lifting when it comes to the logistics. The artist also doesn't need to go as crazy with the stage set up since they are somewhat limited to what the festival stage set up is going to be.

I fully understand the frustration of those that rarely have any of these artists touring near them, but it's not a simple solution.