I'm the second-most experienced immigrant that I know. Although as a white British woman I've tended to be described as an 'expat' rather than an 'immigrant', personally I'm fine with just being 'foreign'. This is what I've learned while living overseas.
1. The United States of America does not celebrate Bonfire night. Watching my first 5th of November sail by without so much as a sparkler was quite traumatic. Clearly I hadn't considered that the US was founded in 1776, whilst Guy Fawkes was busy plotting way back in 1605. When they did bring out the fireworks on the 4th of July I couldn't fully embrace the tradition as they were celebrating independence from my homeland. Yay.
2. Staying with the US, I also never fully understood Thanksgiving. I have an inkling that Americans like it because while it's in the holiday season, it includes everyone regardless of religious beliefs which appeals to their pre-Trump feelings of political correctness. For me the Pros for this holiday were: Two and a half days off work (the half was unoffical, but no-one works a full day on the Wednesday before); inflatable baloons; turkey and cranberry sauce; pies; Black Friday (online only), oh and sometimes it would coincide with my birthday which was always good. While on the flip side: Green bean casserole, this is just so wrong in every way, its only redeeming feature is the fried onion garnish; Black Friday shopping (if you leave your house and get attacked in Walmart); it must be an annually annoying event for American Indians; and traffic, it's so bad, the whole lot of it, cars, trains and planes.
3. Sometimes a country is just not a good fit even though you give it your best shot. This happened to me in Australia. All of those hard-working yet relaxed Aussies that you meet in London? They are the ones with passports. The cost of living was ridiculously high because of the inflated Sydney property prices, imported food and high taxation. When you add in all of the things that are trying to kill you, it becomes even more unappealing. There's the rip-tides on the beach, red back spiders 'Always check the kids's bikes before they get on them!', blue bottles (jellyfish with a sting that can stop your heart), skin cancer 'Hat! Slip, Slap Slop!', cockroaches as big as shih tzus. It's no wonder that I created Little Britain as soon as you stepped into our house in Coogee. Sydney is the only place where I felt homesick, luckily we were fortunate enough to get out.
4. As a woman who'd moved to Singapore because my husband had taken a job in that country I was known as a 'trailing spouse'. This makes me sound as if I'm stuck to his shoe like an annoying piece of toilet paper. The other spouses that I met there all seemed to have recently taken up running, or worse, triathlons. Given the choice of being a house-wife (with a full time live-in maid), finding a job, or training for triathlons, I opted for the job. I worked in an environment which was approximately 70% local and the rest was foreign, mainly from the UK. I'd never come face to face with stereotypes and generalisations of white people before. It would have been funny if it wasn't so frustrating. As an immigrant it was very clear that the Singaporean system was geared towards supporting the locals, for example, ridiculously low taxes if you were working and the mother of Singaporean child, or government housing being heavily discounted. Despite feeling like a second class citizen I loved living in Singapore, even though each day definitely had a 'Groundhog Day' quality to it that you don't find elsewhere.
5. Now we are back in the UK despite the UK government's best intentions to make it very difficult for returning British families to live together if one party is not British or European. Given that non-EU immigration is the only kind over which they can exercise control they've made it both painful (hand-written 76 page form) and expensive (£811 application fee and £200/year healthcare surcharge) to live here. To be an immigrant in the UK at the moment you have to really want to be here, as it's not in any way welcoming or encouraging to talent or skills. To date we've spent thousands of pounds to keep our family together. Being an immigrant is uncertain, uncomfortable, expensive and challenging, it's not for the faint of heart particularly in this country post-Brexit.