Even in Belgium, one of the highest density countries in the EU, most existing and newly built houses are semi-detached, with about twice as much semi-detached + detached houses as there are terraced houses.

In France, terraced homes are rather uncommon outside the North close to Belgium, and old city centers. In fact, I don't even know if we have a name for detached houses, as far as I know they're just called "a house" while a terraced house is a "city house".

So I don't have the numbers for all of the EU but I don't think most homes are actually terraced homes in the EU.

And people do have grass lawns, but only where grass actually grows without too much care needed. Where I come from on the coast grass doesn't grow well on the sandy ground and lawns are uncommon, but a few kilometres inland if you don't do anything you get a mostly-grass lawn, with a lot of clover, daisies and often orchids growing in it.

> I'm the EU

Wow, sounds large. But fitting dropped word for such a big generalization.

People all over the world water plants with water that is not potable itself due to bacterial or viral contamination. This is where the old traveler’s adage “Boil it, cook it, peel it, or forget it” comes from.

If the groundwater is not potable because of e.g. arsenic or pesticide contamination, I think that homeowners are usually aware of that and therefore are more likely to use the water only for washing purposes.

My friend has a condo in the Virgin Islands where water isn’t in high supply (majority of water is sourced from rain)

The HOA where the condo is has an on-site water sanitation facility which recycles toilet, shower, sink water.

They don’t consider the recycled water potable, but I guess they consider it safe enough for watering plants, for re-use in toilet water, etc.

TLDR: in the above case, it’s bacterial risk or the use of a water sanitization facility that doesn’t provide guarantee around portability.

I went with a native grass and my watering is down to 1/4 what it was before that. the grass does go dormant and turn brown in the summer/colder winters though, so it's not as pretty but it is what it is, and HOA allows "xeroscaping"

Many lawns in the US do use grass native to that part of the US. Not all, but many. However grass goes dormant when it doesn't rain for a couple weeks and people don't like that brown look so they water even though the grass (either native or imported) doesn't need it. Likewise people don't like flowers and other weeds and so they apply a lot of chemicals to the lawn - but the grass doesn't need them.

TL;DR: lawns in the US do not need any resources. It is "perfect lawns" that need a lot of resources.

Wow I am surprised monsanto etc. hasn’t come up with and patented a seed to work well on US soil (pun intended)

What is the species that is not native?