> You can't just tell every country in the world: please don't interfere with our opinions!!! We want our people to only be influenced by ourselves!!!

You can indeed, and countries do indeed have laws governing this, as does Romania[1]. The sources of spending for electoral ads have to be very transparent, and adhere to various regulations, such as that foreign governments, institutions and companies cannot finance local elections.

[1]: https://legislatie.just.ro/Public/DetaliiDocument/73672