Never had the luck to visit Europe, have traveled a lot in Mexico when in the Coast Guard but have been to a lot of places in the US.
Seattle is wonderful in August and September for sure. You can see why its called the Emerald City or, like Rome a city built on 7 hills. Great shopping and always something to do or see. Uwagimaya's downtown is a must visit anytime of year. Where else can you find rice cookers from $10 to $700? And like I told Scott you can't find better food anywhere than Seattle.
But for summer its hard to beat Eastern Washington and that includes anywhere in the states. Warm to hot summer days, little if any rain, and great variable scenery. Winter? I hate it more every year.
November/December/January the Gulf Coast of Florida is great. Visit Tampa now and then for lunch and perhaps a trip to Orlando to visit the Cheyenne Saloon or Disney World. The little town of Belleair Bluffs was great for us. Close to Tampa and the gulf, great people and warm breezes. Those same breezes are miserable until you get used to them in the spring/summer.
One thing we have done most years till this one is visit Seattle in late January or February to get a break from the winter weather here. With surgerys and the problems with dog deaths in the Redmond area we are staying home this year.