The amount of phone storage can be deceiving. What really matters is how much free space is left over. The Android OS takes up some of the storage space and so do apps. Some phones have "bloat apps" that are not easy to remove.
I used a Android with only 8GB of internal flash storage up until a month ago, for every day use. It was still quite usable, but as apps get larger I was starting to have space issues occasionally. I could see the writing on the wall. But for a travel phone it would have worked just fine if I had only a few apps on it.
However, my old phone didn't have much "bloat." Some of the newer cheap phones with only 8GB might have less free space because there are so many junk apps you can't easily remove. On the upside, if you add a microSD memory card, Android can use "adaptive storage" and use some of the extra space you add for apps, something my old phone couldn't do.
My new phone, a Moto E4 (fully unlocked) has 16GB which seems more than enough for me though some people scoff at that "small" amount. (You can add a 128GB memory card too.) The phone retails for $129 and is a super nice phone in my view. There's a similar version on Amazon for Prime members for about $100. The real reason to spend more than this for a smart phone is for a better camera in my opinion. I don't plan to use my phone's camera for much more than snapshots and use a real camera for "real" pictures.
I should point out that not all phones that work in North America will work overseas - or work well. We use different frequencies in North America that are used in Europe. Your American phone may work in Europe but may not have all the frequencies to pick up the fastest data networks. You may not care at all about this if you are not doing much with the phone...but some people would care. I know I did, because I found my old phone very frustrating to use in Europe because it was so slow, even though it was "fast" at home. But you can check the phone's specs and see what frequencies it has. It needs GSM 900MHZ/1800MHZ to work at all for voice calls and at slow 2G data speeds, and if it has UMTS 900MHZ/1900MHZ it should work as at least 3G, which might be acceptable. LTE is the fastest; I think LTE band 7 is used in many European countries.