I can't help you out with USC or Rosalind Franklin specifically- I suggest you take your question to the school specific forums for those schools.
Anyways- I think the general rule in the states is that they count all of the undergraduate courses that you've taken. If you're doing a second undergrad, I'm going to guess that you will have six years of undergraduate education under your belt at application time; American schools will calculate your GPA using all of the courses that you've taken in the past six years.
Just so you know, some schools in Canada have...for lack of a better term...grade forgiveness programs. Western will look at your GPA for the best two years (provided that you have an 11 in verbal), Queens averages the last two years, U of T will drop one full course for each year you were enrolled (so they would drop 6 credits for you...or 12 single semester courses), Ottawa has a weighting formula that only looks at the last three years (for you this would = ((4th year*1) + (5th year*2)+ (6th year*3))/6)). Other schools across the country may do similar things, but I don't know because I didn't apply to those.
Good luck with your application process!
