Don't think there is any connection between the two visas, you can't be in two places at the same time , and each place has it own rules on immigration, obviously one get invalidated when you over stay outside the country, as far canada is concern I think you can stay out 3 years in 5 years time, so no problem but the US visa is much more strict, and I think you have to be in the country for 180 in every year and much more rules...... none of these countries care how many recidency you apply for, its the time you stay out it get invalidated automatically,
how to they know ??? every move is recorded when you travel in and out,
when you go for you US visa stamping you can have recidency from Australia,Germany,Canada .... and so on, no one cares..
But here is what you can try if you have canadian immigration already, you can apply a CP instead of 485, 6 months you will be out with GC