Solar and battery for small usb camera
Use a buck converter as others have recommended. Car adapter to USB will work. This reduces the cameras current draw from the battery down to about 1 Amp. (5V*2A = 10W = 12V*0.8A) You must upgrade the battery though. AGM will give you longer life than regular sealed lead acid. 12aH is not enough as this only gives you 12 hours of run time when the sun goes down which means you will lose power on any rainy or cloudy day. You can get a 40Ah AGM battery for about $100. A 50W panel is probably passable with 6 hours of sun per day. 50W - 10W camera = 40W * 6h sun = 240Wh vs 24h day - 6h sun = 18h night * 10w camera = 180wH night usage. This means you gain about 60wH per day under good conditions. 100W panel would be preferred though if you have the space.