No, it is not considered rude to cut a steak with a knife and fork in the United States. In fact, using a knife and fork to cut and eat a steak is the standard and expected way to do so in most formal and casual dining settings.
In the United States, table manners are generally influenced by European etiquette, where using a knife and fork for cutting and eating meat is the norm. Cutting your steak with a knife and fork shows that you are following proper table etiquette and dining in a respectful manner.
Using your hands to eat a steak is considered less formal and is generally reserved for more casual settings or when the steak is served in a finger-food style (e.g., sliced or served in smaller pieces). Even in more casual situations, some people may still prefer to use a knife and fork for cleanliness or personal preference.
It's essential to be aware of the specific dining environment and the behavior of those around you. When in doubt, follow the lead of others at the table or opt for the more traditional method of using a knife and fork to cut and eat your steak. Doing so will not be seen as rude but rather as a respectful adherence to dining etiquette.