Note: while I learned French for a couple years and hopefully have gotten a decent grasp of grammar, it’s been a while since I learned French seriously and (as might be guessed) I’m not a native speaker (and do not have the proficiency of one).

If I remember correctly, ce (and the appropriate plural/feminine forms) can mean both this or that in English, depending on the context. Comparatively, ceci and celà mean this and that respectively, but are only used as pronouns, and not as demonstrative adjectives.

Thus, your translations of the sentences into English seems to be correct, although without a more specific context, I would be inclined to read the second as These [women/girls] are Spanish. Since the nationality has to be inflected for gender, there is also an implicit piece of information there, although technically speaking “This is an [male] Italian” and “These are Spanish [females]” is still correct. Comparatively, if we had ces sont des espagnols, we wouldn’t really be able to conclude anything about “these [people]” apart from the fact that “these [people]” contains at least one male.

(Also as a side note: as a native English speaker, I would say “this is an Italian”, for instance in “This is an Italian. He takes the metro to work every morning and drinks espresso at lunch.” While I might not say this much in normal conversation, I would probably use it at the very least in writing, perhaps to achieve a certain style.)

as a native French speaker I’ll try to explain with more details the correct meanings and translations. Note that I’m not a native English speaker, so I cannot guarantee a 100% my translations 🙂

C’est un Italien.

means in english This is an Italian, which is different from:

Il est Italien

which means He's Italian.

Ce sont des Espagnoles

Means These are Spanish girls

In this case, Ce sont is identical to C'est but is the plural form, used because there are more than one Spanish girl. We know that they are girls because Espagnoles has a final e (not Espagnols).

These [women/girls] are Spanish

shoud be translated by Ces femmes/filles sont Epagnoles which really means these ones.

As an example,

Regarde les filles là bas, ce sont des Epagnoles, mais celles-ci sont Italiennes

should translated by something like Look at the girls over there, these are Spanish, but those ones are Italians

The construction is ce, plus a form of etre, “to be.”

The third person singular construction is ce est, (he is), which contracts to C’est. C’est un Italien. He is an Italian.

The third person plural construction is Ce sont, (they are) with no contraction. Ce sont des Espagnoles. They are (some) Spaniards.

(Des is a contraction of de and les, and “de” in this context functions as an “adverb of quantity.”)