First, it helps to post a map that includes modern borders so we know which cities get dumped into the ocean upon arrival. Additionally, its important to pick a date within the almost hundred million years that is the Cretaceous, so that we can use the proper maps, as NA goes through a great deal of transformation via the mid-continental ocean.
So just using the map I posted, a great deal of the country that comes basically any coastal city, anything from the south, the plains states, and such are completely fucked. What's left? Rocky Mountain places, Appalachia, the Great Lakes region, and Seattle. None of the great agricultural centers of the US make the transition. Oh and several of these areas are home to active volcanos now.
So survival and tech level. Most die within a year. Outbreaks of disease, starvation, warlordism, predation, and a huge number of other issues means that most people die. Agriculture will get started, maybe, if any modern foods came with, but if they didn't you can verifiably say that humanity died within the next decade. Quite plainly, none of the cretaceous plants will have the same nutritional value modern ones have.
Humanity will be driven to primitive tribal structures, if it survives.
Oh and I haven't gotten to the part that sucks for everyone and likely kills a bunch of people. It's hot, all of the time. A high oxygen atmosphere, in the worst predicted outcome of current global warming. Tropical oceans average 100 degrees at the surface. There is little wind, and oceans are stagnant. Sealife killing events are common, with huge areas suffering complete loss of water oxygen, suffocating all marine life.
Being ported back to the Cretaceous sucks, and you wont even see, and die by, a fucking Tyrannosaur Rex because they evolve in the last few millions of years of the era.