Hello,

You were able to enter because the giveaway's region restrictions include your Steamgifts country.

If your Steam country doesn’t match your Steamgifts country anymore, you should create a ticket to have it changed.
Just create a ticket with a title like "Country change" and attach a screenshot of your Steam account details showing your selected country.
You could upload it on postimages or imgur, then post the link in the ticket.