American, here. Got a bidet, and I am never going back. The fact that this isn't standard in American households is disgusting.

I set all my digital clocks to 24hr mode, something I picked up after living in Europe. Would never go back.

Before I quit drinking I believe I was following Russian culture with my vodka intake.

I cross my sevens like a German.

I'm British and I say y'all fairly often. It just rolls off the tongue.

Stretching. I think this originally came from southeast Asia, its so far back that its hard to discover. But I stretch every single morning. As a Native American I need that to limber up so I can dance, which I enjoy doing.

Sleeping on a thin futon laid out on the floor (Japan / Korea). And riding a bike or e-bike everywhere (Netherlands), even though US cities and infrastructure are hostile to humans

I've learned from the Japanese phrase 'itadakimasu,' which is said before eating as a way to thank the person that prepared the food. I think in the west, a lot of us grew up learning to say things like grace before a meal, but that is too religious for me and gives God credit for peoples' hard work instead. I love the idea of ritualistically thanking the people who actually made the food. It was one of the things I appreciated while studying there that has stuck with me.

I heard Koreans use metal chopsticks and bought pack home. Took some time to learn how to use those but so much easier when I can put those in dishwasher.

I would LOVE the house slipper bit. I've suggested it so many times. Wife and kids just won't go for it. Wife says it's rude to ask a guest to take off their shoes. I disagree but she just can't see my point or view. If you want to enter my house, show respect and take off your shoes to keep my house clean.

From the USA: wearing a white t-shirt under my shirt or t-shirt. Helps preventing sweat stains under armpits. Really hot in the summer though

I wear a mask unless I need my mouth for something.

I'm a big white guy but I wear sarongs all the time, having grown up on Java and wore them as a kid. Soooo comfortable and versatile.

I was what I think we would now call a "weeb" in my junior/senior year of high school, and had studied Japanese culture before making a short trip over there in the summer. One of the things I learned was that blowing your nose in public is seen as bad manners, and it really stuck with me. When you think about it, it is pretty gross to loudly blow snot into a tissue (bonus points for carrying a handkerchief!) in front of others, like (as an American) we'll just do this at the dinner table without batting an eye.

To this day, I try not to blow my nose in public places or in front of folks if I can avoid it, because it has grossed me out ever since learning how Japanese culture perceives it.

I am not Jewish, but I have adopted the practice of placing stones/pebbles on my parents' gravestone each time I visit.

I adopt representing 3 with thumb, index, and middle finger (German?), Instead of the usual index, middle, ring. This is easier for teaching my little girl as her hands muscle aren't fully developed yet and have a hard time controlling her ring finger.

A few jump to mind.

I say No Worries quite a lot.

I use chopsticks as much as a fork at home.

I take my shoes off inside.

I'll order a Pint.

I drink Yerba Mate, and I'm from Australia

I was raised in an extremely conservative Southern Baptist Christian tradition, but I often recite the Hail Mary and/or the first line of the Shema (in admittedly very poor Hebrew) when I pray. There's something about knowing that the same prayer has been prayed by millions and millions of humans through history that makes me feel more connected.

My wife and I celebrate White Day, or at least a version of it. She buys/makes a gift for me on Valentines, and I buy/make one for her a month later.

Doesn't really change much, but it's a fun little twist.

I've lived in Japan for a long time. I make a lot of Japanese noises now.

I never show the bottom of my shoe and think less of those who do. Learned this while traveling in Asia.

edit - Example of this is kicking my feet up on a stool at the local pub.