Delta used to have B757 service to Vancouver from Atlanta, and possibly SLC. But, now they have stopped all service to YVR except for RJ service to Seattle operated by a Delta Connection affiliate.
The dispute with the B777 is that Delta and the pilots can not agree on pay per hour for that aircraft. If it doesn't get resolved, DL will likely cancel all B777s. I hope that they settle the dispute because I'm sick of all the transatlantic jumps on the old B767-300ERs.