Question about Morgan's quest line

[Killer7181]

Ive just finished the quest "Finding Steve Linney" and I have a choice to do other nation's quest..
If I choose to finish Morgan's Line quest first can I still do the other nation's quest??

By the way whats the next quest after Finding Steve Linney?

 

[woopypooky]

next quest would be the last quest. Attack of Panama by 5 great pirates.