is $7000 enough money to travel europe for a 2 months?

I want to travel the following countries:
Italy, England, Ireland, Belgium, Nederlands, France, Spain, Germany, Greece, croatia, Hungary. I plan on staying in hostels and either flying to each country or taking a train. I havent decided on that yet. I dont require much. But I want to make sure I have enough money to enjoy europe fully.

If you are an american citizen, what do you need besides a passport to travel europe?

I’m planning on flying into Britain and then I want to travel to the European Union. Is travel between britain and the EU fairly simple? I’m finding the best priced tickets into London, but I don’t want to stay in England, so I just want to know if its no problem to just cross over into France and travel the rest of Europe.