I visit the states yearly pretty burned out on the place at the moment, outside this year leave for europe in a month for 4 months. But generally LA is a shithole, its a bit of an eye opener for those visiting for the first time stepping off the plane picking up the rental car very first service station tellers are behind bullet proof glass. Also remember when you rent a car you have to prepay before filling up, I've found this applies everywhere in the states. A bit annoying when you're trying to refill when returning, but you can go back in and get cash back. San fran is pretty dumpy to. I agree with Universal but I love Universal over Disney, Universal Miami is awesome.
If you're renting a car, use this
https://turo.com/ Allows you to rent big V8's for cheap and I always go this route when driving to Vegas. There's a tone to do in Vegas even if you don't gamble, and be wary of staying places to short a time because you'll feel constantly on the move. A week in Vegas for sure.
New York for the first timer is a must of at least a week minimum also, it's an amazing city but again don't worry about the piles of trash everywhere that's just normal without a modern garbage collections system. There is just so much to do, walk the old city tram line, explore central park, there's always comedy shows nightly it's a blast. Don't get scammed by any taxi or ubers at the airport. Get into a yellow sticker-ed taxi at the airport they have flat rates and the cheapest.
I loved Miami just for the theme parks, but these are several hours outside of the actual Miami city. I've only done Miami once and it was for spring break 3 years ago or so? And spent 10 days there. But unless you're clubbing nightly might be wise to skip.
If you're looking at using up 4 weeks I would probably go Hawaii (beautiful fun to do), Vegas, New York and Cuba before flying back. There's flights to Cuba easily now and it's on my bucket list before it changes to much. The U.S is very much alike to Australia, once you've visited one capital here and there they are all very similar experiences nothing ground breaking. The southern and northern states outside of tourist areas would be great to sight see but you're then talking 3 months with a car etc and exploring the entire country.
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So personal opinion think outside the box a little, Hawaii, Vegas, New York, Cuba. And you will have had an awesome experience and seen a lot of what the best the U.S has to offer.