Other sites have an option to close questions. Why doesn't the Spanish one have this? This Meta has it, but the main site does not.
It has it, only that you don't have enough reputation to see it:
Help Center > Privileges > Cast close and reopen votes
Awarded at: 500 reputation
Once you reach the 500 points you will be able to see the
close option below every question. In the meanwhile, you can do it through another privilege you already have:
Help Center > Privileges > Flag posts
Awarded at: 15 reputation
Flagging is a way of bringing inappropriate content to the attention of the community. The currently implemented flag types are the following:
- Flag to close (questions only)
Regarding you having this privilege in Meta but not on the main site: it does not have to do with being in Meta or main, since privileges are the same in both. It has to do with you being the owner of the question. From What is a “closed”, “on hold”, or “duplicate” question?:
Who can close a question?
Users with at least 250 rep may vote to close their own questions
Since you have 445 points now, you are exactly in the position of being able to close your own posts but not others'. I cross checked with some accounts I have in other sites and it is the case.
I'm not an expert on this, but I think this is what's going on: when a user account hasn't yet reached the threshold for being able to vote to close a question (500 pts), the word "close" won't be visible. EXCEPTION: apparently the threshold for seeing the "close" button on one's OWN question is lower (250 pts).
I took a look at a site where I have between 250 and 500 points in reputation. Here are screenshots: