What is the easiest country for a westerner to move and adapt to?

If you can speak a foreign language then as the other guy pointed Australia and New Zealand but quite a few Europeans (Westerners) have moved to Latin America in hopes of a better life and more opportunities. Argentina is full of White European immigrants.

Other options include the Philippines, South Africa (can be a bit dangerous though), and Northern Europe.

I've lived all over the world, and the easiest places to assimilate into the culture is one that speaks the same language. So if you're an English speaker, look at the UK, Australia, or New Zealand. I've been to the UK and Australia, and while the culture is quite different, you can understand most of what they're saying, so you can pick the rest up quick. I loved my time in both the UK and Australia.

Now, if you can speak a foreign language proficiently, you could go for one of those countries. I personally loved South Korea and I'm currently living in Japan, but the language barrier (and my difficulty learning languages) has made it a bit more difficult.

If nothing else, take a trip, apply for a working visa, and check some different places out. You won't have to give up your US citizenship and you can "test" out other countries by working and living there.

Best of luck.

i say stay and watch the life you once knew crumble around you before your very eyes