One hour can be enough but close particularly if where you are going is near the top of World Showcase (like Japan, Germany). Bus ride takes about 20 to 25 minutes. Walk from bus through Epcot entrance to base of WS takes about 12 minutes; walk from base of WS to the top where the American Pavilion is takes another 15 to 20. Big issue is whether you will actually catch bus as planned. Busses from WL to Epcot theorectically come every 20 minutes (and often they do although sometimes longer)--if you show up at WL bus stop just after one has left you could have 20 minute wait for another.