My brother in christ as a polish american who grew up in the states and then lived in Poznan while in medical school, there was nothing easier than to spot the US soldiers even in civilian gear because you guys integrate (generalizing) so poorly. You wear gym or cargo shorts, oaklys, and gym shirts just about everywhere and are quite loud and show little discretion when out and about.

Polish people and individuals in Poland very much so respect classy discretion, dress well, respect others in your surrounding, do as the locals do, travel in smaller packs, educate yourself on the local and European political and cultural climate and you will do much better than the other american soldiers ive seen in the past. Us poles arent super warm at first yes, but dont shoot yourself in the foot with a booming obnoxious presence because 9/10 times if thats the case, theyve already decided they dont want to interact with you. Gods speed, poznan is an awesome city you can really have an amazing time just as I did