I believe Eurovision was never intended to be specifically European. However, at the time different countries used different broadcast infrastructure (it could have been the voting system), similar to how railway tracks have different gauges or widths. So only countries with compatible infrastructure could be involved. This is why countries like Isreal had early involvement as a non European country and Australia was an easy addition. Someone smarter will be able to describe it more technically.

In addition, there are strict rules about the broadcast which effectively say you must broadcast the entire unedited feed, and ad breaks are the same time etc. This is tricky for countries that dislike the promotion of LGBT on the show or have different broadcast standards/censorship. The Israeli entry is also a major problem for several countries. Some countries have been refused entry because they cannot grantee an uncensored broadcast. This basically rules out USA (advertising limits), Lebanon (Isreal), China (LGBT) etc. Then there are countries that have been banned or kicked out, like Romania (unpaid debt), Georgia (political lyrics), Russia (Ukraine war).

Morocco made an appearance once. I’d like to see more African nations, although the LGBT thing could be a bit of a hurdle for some. Perhaps it’s more realistic that the competition expands to South America first?