This is one of the major challenges of touring, which I hate in the US and Canada. The problem s not just confined to camping but hotels too. You really never know if you are going to need a reservation or not so you need top make them. If plans change, weather turns bad etc then you are usually stuck. You have to stick to the plan or you spoil the whole itinerary. Outside the US, I have only toured in Italy, Switzerland and Austria. I love touring there because you always have the option of getting on a train to get you to the next town where they might have a room or cmapsite.