The breakable blade of an utility knife is 0,50 mm (just checked).

The diameter of a two tips toothpick is 2 mm (just checked).

I don't know if I'd call it sad. Standard objects of comparison can make numbers and communication more clear.

I get a little tired that it's always SPORTS but things are standardized in sports.

Frankly I wish I had a list of small object that were *globally* familiar that I could use when asking people the size of the ant they saw.

I need:

Something about 2.5mm long
Something about 1cm long
Something about 1.8cm long

Any ideas?

Although Spain uses the decimal metric system, for some time now, when news programmes want to convey to the public just how large an area is (for example, a piece of land that has caught fire), they say: “An area equivalent to X football pitches has been burnt.”
Sad but true.

American artists are great because I think it really captures the fanciful impression of these mythological items

that's because these are fruits and vegetables, which Americans don't eat because they are too healthy, and thus aren't familiar with them

(/s)