• East coast: old money, lots of drinking, cold weather, violence, power, liberalism, deciduous forests
• Southeast: southern hospitality, shithole school systems, conservativism, sweet tea, food influenced by french cuisine, nascar, lush vegetation
• Southwest: cowboys, ranch homes, cultural mixing with Mexico, drugs, art, desert and mountains
• West coast (basically california): hollywood, progressivism, new money, asian-pacific food influences, hippies, poop, surfing
• Northwest: best weed, created grunge genre, rainy, dismal, chill, northern european food influences, rainforests
• North-middle: liminal space, copy-pasted terrain, independent/libertarian, wheat, sparsely populated
• Midest: mix of conservative and liberal, plains farmland, cozy houses, desperate to define itself culturally (see Chicago architectural publications), corn, soybeans, and pigs, neutral accent, german and polish food influence

source: memory

I recommend https://colinwoodard.com/books/american-nations/ It's a well written source on this subject. Woodard details eleven groups each with a shared cultural background, with names like New Netherland, Tidewater, El Norte, and the Left Coast. The Wikipedia page for the book has a broad outline of the ideas if you want an overview; but, the book is well worth a read if this is an area of interest for you.

I couldn’t resist… But Wikipedia should have tons of info on exactly this.

I'm not from USA so I won't answer your question directly (other posters are better for that). Instead I'll point out a few things, based on knowledge of Linguistics plus other stuff:

• Cultural differences are somewhat objective, but how you split the cultures is subjective. As such don't be surprised if different maps show different divisions.
• Language usually play a huge role, and isoglosses are often used to demarcate cultures. However, people shouldn't confuse dialect+language with culture, as it's perfectly possible to lump together two populations of different dialects as the same culture, or to split a single dialect into multiple cultures. Also, dialects themselves tend to be subjective, like the above.
• Geography does play a role too, but it boils down to interaction between settlements and identity. For example you're more likely to contact the guy in the other city (thus share the same culture) if there's just plains between your cities, instead of a big fucking mountain.
• A good place to look at the cultural divisions is the original settlements. Based on that I think that it'll be easier to demarcate cultures in Eastern USA than in the West.
• More often than not cultures don't give a fuck about government borders. So don't be surprised if some cultures grab "chunks" of USA plus either Mexico or Canada.

There is a good general summary here.
https://www.washingtonpost.com/blogs/govbeat/wp/2013/11/08/which-of-the-11-american-nations-do-you-live-in/

The cultural regions are New England, the Mid-Atlantic, the South, the Midwest, the Mountain West and the Pacific.

Politically the South and Midwest are conservative. New England, Pacific, and Mountain regions are liberal. The Mid-Atlantic is a mix.

Cultural differences are largely based on popular religions or lack of religion.

That's about it, Americans are pretty much all the same no matter what state or region you are from.

You're not going to get quality answers here but it might get you started. You will get broad strokes that obscure a lot of difference. If you want to go deeper there are many directions to go in. For example you will want to think about whose perspective you're looking at cultural regions from, because the subsection of the American population you're talking about matters due to segregation, different migration patterns, etc. If you are talking very mainstream dominant culture then I would personally look up US historical trends of waves of colonialism spreading West and events like the Trail of Tears, Louisiana Purchase, Spanish-American War, amongst others that were really big in the establishment of cultural differences. A good chunk of the different cultural regions correspond to bioregions and the culture of the people who were genocided so settlers could take their land. The grease trail is a good marker for cascadia as a cultural region IMO. But the white supremacist settler idea of the "american redoubt" roughly tracks the same region. Cultural regions in the USA are subject to cultural imaginings, it's a lot less regulated than in Europe with your DOCs.

The density of different cultural regions varies by region with population density and degree of diverse migration. For example, the diner culture of New Jersey is something unique in itself, or so I hear. You get wacky foods like skyline chili or the pizza of Altoona, PA or architecural flourishes like the free-standing basement toilets of Pittsburgh. Random ass cities will have their own long standing cultural thing in the states "back east" where the majority of settler Americans live. Whereas the state of Oregon is the size of the UK & contains maybe three cultural regions if you include the state of Jefferson which is kind of just neoconfederate crankery.

But basically I think the whole question you're asking can't be summed up quickly and understanding it requires understanding a lot of history, geography, and politics to get why this country is as fucked and fabulous as it is. Like I could rattle off a TLDR of stereotypes of regions like the rainy PNW, polluted and expensive California, the snowy Rockies, the sunny Southwest, the corn covered flat Plains, the behemoth Texas. The "midwest" is somewhere between the plains and the Great Lakes Region, which bleeds into mid-atlantic to the east and new England to the NE & the South to the SE. On the eastern seaboard you got new England, mid atlantic/DelMarVa, then the South then Florida which is its own beast but also contains multiple regions. But even this is oversimplifying leaving out regions like the Big Thicket between Texas and Arkansas and Appalachia, which stretches between multiple regions as defined by states but is definitely its own cultural region, as is Acadia.

TL;DR: tough question, maybe not the right one, depends on who you ask.

Recent political shifts have substantially pitted "heartland" (Central states) against "coastal elites"; "heartland" is depicted as rural/traditionalist/uneducated whereas the coasts are rich and intellectual (with negative connotations for both)

It seemed every time we drove 100km, the yanks had a different name for cider (the alcoholic fermented drink, not fruit juice, although probably that too, seeing as "cider" sometimes meant nonfermented fresh fruit juice), a different name for fizzy drink and a different name for sausage… and so on. The boundaries were definitely not along state borders. Etymology maps of the US must look peculiar.