Linguistically, Spanish and French are Western Romance languages and technically should be closer to each other than Spanish and Italian. However, French also underwent certain significant changes (possibly due to Germanic and/or Celtic influence) that most other Romance languages didn't, hence why it seems more "foreign". But there are a lot of common things between French and Spanish that Italian doesn't share (e.g. the way plurals are formed with "s", or particular sound changes, like adding "e" in front of certain consonant clusters, c.f. Spanish "estrella", French "étoile", but Italian "stella")

> But as far as grammar, they seem to be almost identical.

Apart from the different plurals, probably the biggest difference to me seems to be that Spanish has three different past tenses, including indefinido, while the corresponding tenses in Italian and French (passato remoto / passé simple) have completely fallen out of use except of highly formal contexts (or, in the case of Italian, certain Southern dialects). Instead you'd just use the perfect.