Power steering

Neither one should be affected by an impact. Do I understand the power assist returns at higher engine speeds? That suggests a weak pump but that's due to wear and high mileage. You might start by checking the drive belt for the power steering pump to be sure it's tight. If it is loose and slipping, the jar might have cause the spring-loaded tensioner to bounce and stick in a partially released position due to rust buildup. If that tensioner is working properly, you should be able to pull on the belt to make the tensioner move on its pivot, then it should spring back when you release the belt to take up the slack. If it doesn't spring back freely, replace that tensioner.