It would be interesting if anyone has any insights on this one. Raoul brought this up on another thread and got me to thinking.
The word "preserve" just means to be kept alive, it doesn't mean that everyone in Portugal will be living the Faith.
Our Lady might have told this to the children so they will not lose hope. Hope for us all, that there will be places in the world where the Faith will be kept alive. By her mentioning only Portugal does not mean it won't be kept alive in other places in the world, but Portugal was the place best known to the children, their home. After all she was speaking to them at the time.
We seem to think that just because Our Lady mentioned Portugal it has to be the PERFECT place for the Catholic Faith. In reality, the devil is there more so than other places, since he too heard her words. The truth is she did appear there and gave her message, now it is up to us to obey her requests, and trust that in Portugal the Faith somewhere, and in someplaces the Faith is very much alive and preserved.