Assuming you have a carbed model of the 08 America. When it is cold, you need to pull the choke (enrichener) out all the way. Start the bike then tap the choke in a bit to keep the bike running at a reasonable idle speed. If needed, leave the choke out with the bike idling higher than normal until the bike warms up. That is how I start and run my ride when it is cold. The bike needs a lot more fuel when it is cold to keep running. Since your bike runs poorly when cold and fine when it is warm, it appears your choke needs to be left out.
Have you modified the bike at all?
