There are a few factors that stand in the way of this setup, but a milder version of this where we are generally trying to tie power grids together to transmit solar and wind power from places with favorable conditions to users is underway. I know for example of at least one large project where Singapore is installing large scale solar in Australia and building undersea cables for transmission (1). So we are going in this direction despite difficulty.

The main issues are:

• Transmission is difficult and expensive. High voltage power lines especially undersea or very long ones are expensive things to construct, and still relatively uncommon and therefore specialized compared to regular grid infrastructure.
• Oftentimes solar in the dessert is actually not that favorable in price especially if you factor in the transmission which is not 100% efficient. The site in the dessert might require security especially in places which are perceived as insecure or unstable and regular cleaning if the dessert is dusty. And solar obviously benefits from more sun hours and no cloud cover, but high temperature eats into that advantage somewhat, as solar cells are less efficient at high temperatures (2).
• The management and bureaucratic overhead rises for larger projects and projects involving several countries which is an issue for both regular grid interconnection but also purpose specific generation and transmission involving 2 or more countries.

There are probably other issues but work is being pursued nonetheless.

(1): https://en.wikipedia.org/wiki/Australia-Asia_Power_Link

Other examples I could find with a quick google:

China: https://www.renewable-ei.org/pdfdownload/activities/GEIDCO_191126.pdf

EU: https://ember-energy.org/latest-insights/breaking-borders-europe-electricity-interconnectors/

US: https://www.gridunited.com/projects/

(2):https://8msolar.com/solar-panel-efficiency-vs-temperature/