So first of all, the US is big and diverse, if you hop in a car and drive from New York to LA without stopping, taking the fastest route, mostly on major highways, averaging out to something like 60+mph (about 100 km/h) you're still going to be spending just about 2 days in the car.

And in between, you're going to see a little bit of everything, mountain, plains, forest, farms, huge dense urban cities, towns small enough you can barely even call them a town, suburban sprawl, massive industrial facilities, you name it you're going to see it.

Overall, if you live in an urban area, the situation may not be too bad, cities are somewhat walkable, there's public transportation that will usually get you fairly close to where you need to go, there may even be protected bike lanes, etc. although the situation will vary wildly from one city to another.

It will even vary from one part of the city to another. You can have large sections of the city where there's no real grocery stores or other places to get your basic necessities, and you're pretty much limited to whatever you can get from corner stores, bodegas, convenience stores, etc. (mostly pre-packaged and processed foods, and if you're lucky maybe a couple pieces of fresh fruit) and if you want anything more than that you're probably looking at taking a few hours out of your day to walk a significant distance to a store or take public transit that may not go exactly where you need it, may be slow, expensive, or just a pain in the ass to deal with, etc.

Getting out into the suburbs, it's again kind of a crapshoot. There are some walkable suburbs, with wonderful shopping options, there's some that are a maze of residential developments and gated communities that come off of major roads with no sidewalks or even shoulders worth speaking of and you're taking a significant gamble trying to walk anywhere from there. There may be little or no public transportation and if there is it may not be going anywhere you need to go, or be convenient to get onto

Personally, I live towards the rural end of the suburbs, about an hour or less from a major city depending on traffic.

Damn near everything I could ever want or need is within about a half hour drive, and most of I commonly need is covered within about 15 minutes.

If I don't have a car though, my options drop off significantly. I'm looking at an hour walk one way to get to a grocery store, mostly along a long winding road with little or no shoulder and few streetlights. The only things I would really feel safe to walk to are 2 pizza shops, a small hardware store, a bar, a CVS, and gas station/convenience store, those last 2 are going to be about a half hour or longer walk, and along that winding road, but it's a stretch that at least has a half decent shoulder and some lawns to walk on for most of the way.

If you have a bike, there's a decent bike trail that will get you to some more shopping options, but it's about an hour's ride one way.

If you need to catch public transit, you'd have to walk about 2 hours to catch a bus, that line basically runs straight up and down a main road between the city and a larger, urban-ish town further out in the suburbs. There's not many options to transfer to anywhere else along the way but there's a lot along that route so if you can get to that bus most of your needs will be covered, but it doesn't run super frequently and it's not going to get you anywhere in a hurry.

Getting out into rural America, you have some small towns that are functionally self-contained, with their own grocery stores and other shopping options in-town within walking distance. Your options are limited but for the most part everything you really need is right there in town.

If you don't work in town though, and often people in these areas don't, they may be involved in farming, logging, oil/natural gas, construction, etc. and may work many miles from town, you're pretty much screwed if you don't have a car, or at least can count on carpooling with a coworker.

There's other small towns where there just isn't much of anything at all, maybe they have a gas station and a liquor store, and if you need anything else you're SOL, in some cases you may be looking at an hour or more drive to get to anything else so you can forget about walking.

Regardless of where/what kind of area you find yourself in, transportation between cities is often going to be an issue. You can probably catch a Greyhound bus or maybe Amtrak or similar between most major cities, though you may have to get a little creative with figuring out your route, but if you're trying to get to the smaller towns in between you may not have much luck.

There are, of course, nearly as many exceptions and special cases to everything I said as there are individual towns and cities.