There is a Dhammapada verse which has a nice way of putting it:
Dhammapada, chapter 5 verse 3:
"The fool worries, thinking, “I have sons, I have wealth.” Indeed, when he himself is not his own, whence are sons, whence is wealth?’
The bold in Pali :
Atta hi attano natthi ( he ,himself, is not his own)
There is no indication that atta is an illusion, only that it is not yours,it cannot be owned.