I do the same thing. I buy direct from Apple. Use any Carrier I want. USA or Europe. (Orange, BFSR, BiTel, Wind, Vodafone) Just purchase SIM Card. In USA, I useI purchase brand new iPhones from Apple that are unlocked and have used them all over the world with no issues.
T-Mobil. Have used ATT in the past but they became a ****.
Yes, may cost me a little more, but no problems. Well worth it to me.
BTW, present phones are all
iPhone SE (2nd Gen).