Why is there a huge difference in culture practice and habits between countries?

We do... However many things has impact on different cutures...

Human has been living on Earth for thousands of years where all they had was the land they lived on...

They had to hunt, gradually they got familiar with agriculture, then they needed to store what they harvested, so, villages and towns were planned and built... then there appeared religion, and beliefs instead of rules and regulations.... language and cuniforms, trade, roads, civilizations, and.....

All that happened not within a blink of an eye, but over a long long time... that is why culture is deep within us..

Adaptation. On a basic level if you put a group of people in the Arctic and another in the tropics and leave em for a few hundred years you will find wildly divergent cultures as a matter of survival.

At the same time there are intrinsic human similarities that exist no matter what.

Depends, if you just look at the surface there are many differences, if you care to go deeper you'll see we are all the same just as much as we're different.

The term 'culture' wouldn't exist in the first place if they weren't different than each other

Thank goodness that we are all different and not the same. That would be boring as heck.

Societies evolved in multiple bubbles, virtually with no contact at all with each other. What you experience today, is the residual effect of that isolation.

the differences in experiences change everything, from country to country just as they d with individuals in your own culture/country.

substantial differences in some and very familiar in other countries..

It’s what makes the world interesting.

That's the globalism propaganda...