Is this gonna cause any trouble I might not want?
Yes, indeed.
Check here -> If you change Country or Region, you must comply with all regulations described here -> Change your Apple ID country or region -> Change your Apple ID country or region – Apple Support (UK)
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See this Apple article: If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card
If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card - Apple Support
check. ⤵️
Card is not valid
Card has already been redeemed
Card is not activated
Code is unreadable
Code must be redeemed in a different country or region
- You can't redeem Apple Gift Cards or App Store & iTunes Gift Cards outside the country or region of purchase. For example, if you bought an App Store & iTunes Gift Card in France, you can't redeem it in the App Store in the United States.
Contact Apple Support -> Contact Apple Support.
Get more help and assistant from Apple directly, see Contact Apple for support and service -> Contact Apple for support and service – Apple Support (UK)