If you're moving here 'blind' (e.g. you're not going to school or have a job lined up) and you're not rich, I'd suggest looking in some of the small-to-medium cities that you rarely hear about. Sort of the "3rd-division" of US cities, you might say. The "1st Division" would be the ones you always hear about: New York, L.A., Chicago, San Francisco, Seattle, Miami, Dallas, Houston, Washington DC, Atlanta, maybe some others. The "2nd Division" would be places like Boston, New Orleans, Philadelphia, Phoenix, San Diego, Denver, Portland OR, Minneapolis-St. Paul, Nashville, etc. There are lots of low-profile places that have a lot to offer: Buffalo, Kansas City, Milwaukee, Indianapolis, Baltimore, Albuquerque, Columbus, Oklahoma City, etc, etc, etc.
Then are small cities that I think are probably very livable. Just around here, we have places like Albany, New York; Portland, Maine; Providence, Rhode Island; Lowell, Massachusetts. A few months ago I heard the mayor of Erie, Pennsylvania (metro area pop. ~250,000) on the radio literally asking the Governor of Texas to send some migrants there, because businesses were looking for workers. (Of course, he didn't. Sending recent immigrants to Erie, PA wouldn't score any political points or make any headlines, especially after the mayor literally asked for them. It's not the job of Republican politicians to solve problems.) Definitely do your research, though. Some places might surprise you, for good or ill. For example, I read recently that the most difficult city in the US to find a place to live right now is... Worcester, Massachusetts. Where the [fudge] is Worcester, Massachusetts, you ask? It's commuting distance to Boston, is where it is, and as of a few months ago, it had the lowest rental vacancy rate in the entire country.
There are 336 municipalities in the US with populations of 100,000 or more. And that's (a) not counting the "metro area", just the municipalities themselves, and (b) just if you want to live in a city.
Murders.. damn! That's the exact thing I'm trying to avoid. Scratch Chicago and NYC off my list
The violence in Chicago, and many cities, is very dependent on the neighborhood. A few years ago, I saw that Japan had issued a 'travel advisory' for Boston for its citizens, but when I looked, they were referencing crime statistics from one particular neighborhood - which, to be clear, were alarmingly high, but a tourist would
literally have to go out of their way to get into trouble there. I wouldn't get too worked up about either the overall numbers or the anecdotes about random violence on the subways, or wherever. Assuming one knows how to comport oneself in a city, you shouldn't have any problems in either place as a visitor.
If you're thinking about moving to somewhere in the US, you definitely need to research your target city by neighborhood and by metro area. Places like New York City and Los Angeles can in many ways be better understood as several cities, and a number of cities here are part of a "metro area" of several smaller cities and towns that function as one city. Also, the "effective size" of our cities is very flexible and can vary wildly. 10 miles in Los Angeles or Dallas and 10 miles in New York or Boston are not the same thing.