If this is the case then my new day's budget starts 8 a.m. in the UK, which is good. But I suspect that my budget gets mostly used up by surfers over there, and there is no budget left to show adwords in north america (by our morning). I guess the campaigns need to be split by continent.
... there is no budget left
So, why don't you go down with max CPC? Yes, your average position goes down, but also your average CPC.
If I have 100 UISD budget for a day, I prefer 120 clicks for 83 cents on position 4.9, then 100 clicks for 1 dolar on position 3.8. What do you think?
But anyway - it is very good idea to have a saparate campaing for US only.