USA could be complicated and depend on where about you are going. There are lots of food culture there and kitchen management could be a challenge. However, their allergy awareness are very high generally. Eating out is generally safe. Again, you have to make it very clear that you have food allergy. Food size is huge too, I promise that.
I have just returned from Washington DC. I went there with a friend's kid with gluten allergy at the cheese cake factory (a restuarant name). And, they know exactly how to look after us. There is also a place in DC that the owner also has allergy. And, the food is just wonderful.
Flying with United Airline should be fine with peanut allergy. Their food is very basic, and no peanut as snack.
Domestic flight would have no food normally, unless at your order.
