I need help

Hello there. i‘m from germany, currently visiting the US (sorry for my sometimes bad english) and I have a problem.

My Samsung S7 and my german SIM card worked perfectley here. Now my phone died and I need a new phone. I need it because I recieve TAN codes from my bank via text.
I know that I need an unlocked phone but is there anything else that is important when it comes to using my german SIM in the states? The phone doesn‘t need to work in germany, it just needs to work here. Sorry for the question but I have no idea about it.

Kai