They are mostly a problemin the southeast and lower midwest. I never encountered them in Colorado, California, Oregon or other parts of the west, nor in New York or the rest of the northeast.
I’ve never experienced them or even heard of them in California. I had to look up the word to find out what chiggers are, although I vaguely remember hearing about them in my youth in Chicago.
I don’t really want to know more about this, which I discovered in my research:
My grandmother always called the really pretty Asclepias tuberosa “chigger weed” and warned me to stay away from it. I was also once warned while collecting Spanish Moss that it was full of chiggers. But I’ve never actually encountered them, in either plant or anywhere else.
They are horrible in S. Arkansas. Mr.Wrekker keeps my dog walking trails around the place mowed so I don’t encounter them. I still put bug juice on my ankles everytime I go out in the spring and summer. I’m not sure if they are the same but we also have red-bugs that bite like crazy. Witch Hazel will kill them on your skin. But, beware! it burns the bites like fire.
Got three bites on my scrotum when I peed off the side of the freeway in tall grass when fleeing Hurricane Andrew. I was probably 7. Absolutely miserable.
Never heard anyone talk about red bugs in California, and natives here tend to not even know what they are.
Yes we have Niguas here in South Carolina, you must ever be moving, or they will go up on your feet. Now at this time of year where I live you cannot stand still for a moment, but your feet will be strewn with them. This is hard for me now, cause my toe is broken, and I wear no shoes. That is not the worst though; the worst is when you camp, or sleep in the woods; then there is no haven, and they will do the worst violence to you, your legs, feet, and everywhere else you would rather they not; and they will make great red stings all on your body, and they will ache and itch, and you will be miserable.
I grew up in Western Washington (west side of the Puget Sound). We definitely have them. In summertime, you do not roll around in the grass in swim trunks and no shirt or you will be itching all over. In fact I psychosomatically itch as I type this, recalling the feeling as a child.
So yes, they’re up here. And they do remind me of fleas, the way they itch like crazy.
ETA: According to the distribution map on Wikipedia they are practically everywhere in the world, including all of the US.