The recipe is important...
A specific hop variety is not bittering or flavor/aroma. Some are more often used for one than the other, but any variety can be used for any purpose.
With regards to a recipe, however, the amount of hops and the Alpha Acid percentage AND the length of the boil determine how much bittering you get (IBUs). The amount of hops and length of boil (shorter is more) determines how much flavor and aroms you get. (Note that other things affect both qualities, but this is simplified).
It sounds as though you had Willamette for both bittering and flavor/aroma. This is fine. They were probably 1oz packages and if your recipe called for 1oz additions you'll be A-OK. If the recipe showed 1.5 oz and 0.5 oz additions, you'll be either too bitter or too sweet, resulting in an out of balance beer.