If you're looking for easy/moderate base camp cycling in the US, my personal recommendation is the Sonoma Wine Country.

Lots of diversity: vineyards (of course), rolling pastures, redwoods, the coastline. And if you want a challenge, there are a few tough climbs to be had.

Then there's the food — if you like that sort of thing.

Ideal base camp location is Healdsburg, although it can be rather pricey. Nearby Windsor has lower lodging prices.

Sonoma County: Popular Cycling Itineraries



Sonoma County cycling heat map (Strava)

EDIT: Another option for a base camp location is Guerneville, in the redwoods along the Russian River. Considerably more laid-back and "Bohemian" than Healdsburg (the famous Bohemian Grove is actually nearby), it's far less touristy—and it provides easier access to coastal rides.