In Colorado I found three resorts that are around 8,000 ft at base elevation:
Steamboat at 6,900 ft
Sunlight at 7,885 ft
Sol Vista at 8,202 ft
Steamboat is a full blown Ski resort with an airport nearby in Hayden.
Sunlight is just outside of Glenwood Springs and you can fly into Eagle County or Grand Junction.
Sol Vista is in Granby about 25 mile west of Winter Park but you have to drive over Berthoud pass at 11,000 + feet.
I hope this helps.
Can't beat Alyeska in Alaska, where you can see the Turnagain Arm, which is an inlet from the Pacific Ocean. It's practically at sea level. If you don't want to travel that far, then Whistler, BC. is a good choice. In general, the further south you go in North America, the higher the altitude of ski resorts, so Washington, Idaho, or Montana, would be the best bets in the contiguous U.S.