You can leave today. How I did it.
I mean this to be an experience report and hope that it will inspire some people on the fence. I left the USA 5 years ago on literally a whim.
I'm a software person who had been doing a lot of consoling/contracting for a long time so I wasn't tied down to a commute or an office. That was very helpful. If you don't have that, see if you can work towards it is all I can say.
I was living in San Diego and suddenly found myself an empt nester and was looking to downsize. I didn't like my options and on a whim I suggested to my wife we drive over the border and spend a weekend in Rosarito Beach south of Tijuana and while there, call a realtor and look at rental possibilities for kicks.
We met a nice real estate person who drove us around for half a day and honestly the first thing she showed us - a little "villa" on a cliff over the ocean, just grabbed us. It was 1/3 the cost of anything in San Diego of comparable size, and Rosarito is just 30 minute drive from the border. We rented it on the spot.
What made this work was we applied for global entry passes that let us cut the lines for border crossings to 15 minute waits. After living there a bit and integrating with the local expats we found there were a lot of people living cross border lives, working in the USA and living in Mexico.
Lesson 1 - you don't have to get far outside the USA to be an expat and reap the benefits. You can get Global Entry and live a cross border life on constantly renewed tourist cards while you gradually sever your ties to your old country.
After a couple years we became comfortable in Spanish and moved down to the south end of Baja California and cut ties with the USA on a more permanent fashion. I moved our banking to a more international bank, we hired an immigration attorney and got long term residence visas and then citizenship on a pensionado program (you show your IRA statements as your proof of self sufficiency, if you've been contributing your entire career, you almost certainly qualify).
Other things to note - we live in furnished rentals. These are much easier to find than in the USA. You don't need to drag a lot of crap around with you. We move every year to try a new place in Mexico.
Spain has an accelerated citizenship program for Mexicans. We are considering leaping to Europe from here but so far we remain happy as Mexicans. We love the people, the culture, the food, and the cost of living. We are less enthused about the music.
I just wanted to point out, you need not feel totally stuck. You do not need to leap to your final destination in one go. It is possible to just scoot over the border and use that as a lab to figure out how to cut the rest of your ties to your old country before leaping to your final destination. We might decide on Europe for our final move we are still trying new places for now and have not exhausted Mexico's possibilities. Being close to retirement was definitely a plus for me, I'm no longer working, but if you can work remotely you can pull this off. I pretended to work in the USA for years and nobody ever figured it out. I maintained my SoCal residency and paid all my taxes as required as if I'd never left.
Happy to answer questions.
Edit: Thanks for the clarification on Spanish citizenship. I hadn't looked too deeply into it but thanks to commenters it is clear I do not qualify.
There seems to be a misunderstanding that I'm super well off and that this took a lot of money. I initially pursued a move to Rosarito to save money because when looking to downsize from my rented Carmel Valley family house, I didn't find anything I could afford that wasn't way overdue for a remodel. I was paying my kid's college tuition at the time as well and that consumed the bulk of my income. My Rosarito rent ended up being 1/3 of what I was struggling to pay in San Diego and everything else got cheaper too.
I also acknowledge I benefitted from Covid work from home rules. Covid hit six months or so after I moved and remote work was abundant and employers didn't care much where people were. It is also true that I could have just been on unemployment or living on savings and I would have made the same move because it significantly lowered my cost of living from what San Diego cost.
Lastly, it seems people don't really get what deals there are on housing in Rosarito. Here's a furnished beach front two bedroom house for rent for $1350 a month. My first rental wasn't near this nice, my second was kind of rustic and funky but on a better beach. Pretty much the entire time I was in Rosarito, apart from the first few months, covid restrictions were in effect.
You can spend less by moving away from the water or moving into a water front high rise but Rosarito is way overbuilt and inventory is plentiful. I sometimes felt like I was living in a ghost town. I encourage people interested to look at what there is.