freebeer (2018-06-15 10:11:06+00:00): This is a really subjective answer to your question which I have not given yet.
To try and be objective, I will refer you to the well-known page with javascript enabled,
https://resultmaps.neis-one.org/osm-notes
.
On that page, click on the column header by country rank `Open' which will then sort your view by outstanding unresolved notes.
The US of A comes up at the top of that list (we're/you're number one rah rah) but very few open notes, relatively, are due to maps.me abuse.
.
Russia has both a large number of open notes plus a large number of resolved notes, and a high penetration of maps.me probaby due to developer Zverik.  My last scan of opened notes revealed that 1) I am not familiar enough with the language to grasp the meaning in the half-second I give myself per note, and 2) the number of `mi casa' `dom' this week was one, and it didn't even point to a building.
.
Spain shows up high in the list but again the language issue raises its ugly head for current notes, but if one is led to the touristic cities, there is a lot of non-native notes, many due to maps.me, that can stand attention.
.
Iraq is high on the list, but I cannot even get started there due to the language, and what I saw is a large proportion is maps.me notes, and there does not appear to be anyone resolving them.  I would consider that a big issue even though it is off me radar.  This is the case in other arabic countries high on the list as well, showing my cultural ignorance.
.
Poland is almost entirely bug reports in polish and not worth a visit if you're not familiar with wandalizm.
.
At the forefront of the problem countries then is the Philippines.  There is a high penetration of maps.me rubbish notes that I resolve regularly without action, so that it is not as bad as it used to be there, combined with some dubious editing on the map that usually accompanies maps.me (ab)usage.
.
We skip a number of countries to arrive at Cuba, where the ratio of maps.me edits to Real Editor edits is high, with a huge number of unresolved maps.me delete-this-thang notes from long ago corresponding to still-present OSM datapoints.  I pointed you in a notes comment to look at one area where a newbie first did an awful job of entering POIs three or four times in wrong positions which still remain mapped, and then attempted to `clean' things up by opening hundreds of notes along with other maps.me users, which is perhaps the worst mapped area I can point out apart from all the others.
.
Cuba had been at the top of my list for notes issues, but that crown was stolen a bit further down the list by Nepal where a large proportion of rubbish notes can be attributed to maps.me, but the overall general attitude to mapping conflicts with OSM interest of privacy and accuracy.
At least, that is my observation, having closed many hundreds of notes, only recently bothering to actually edit the map data as here.
.
Other countries rank highly on the listing thanks to maps.me, such as Cyprus where a large number of notes in cyrillic script are open with what may well be personal maps.me user bookmarks, a handful of which I've resolved due to parsing their meaning in the half second I allow meself per open note.
.
There are many countries I omit from my listing simply because of the language barrier that may qualify as maps.me notes troublespots.  For this I ask your forgiveness and plead that at my age it is impossible to learn any new tricks or languages, and it's a miracle when I navigate meself to the toilet, to say nowt about the nearest town.