Pririty date is established by PERM submission date. Btw, only those born in china, India, Phillipines and mexico are affected by per country limits (and really only India and China for employment based GC).
So Angola is the same as Canada, Great Britain and Greenland.
This site is a travel site and not best source for these topics: TN and TD info: http://forums.immigration.com/forumdisp ... -TN-Status For US/Cdn taxes and SS/CPP:forums.serbinski.com/index.php US Marriage-based Immigration: visajourney.com