I'm being super-cynical here, so consider yourself warned.
The problem I generally have with using real-world politicians is that when the real politician is featured, usually it's either because the writer is fanboying as he's bought into the cult of personality, or is doing the exact opposite and looking for an excuse to say this guy sucks. In other words, the writer is just looking for a way to insert his opinion as matter of fact, and usually in an unnuanced way. There's almost an expectation that if (for instance) any particular US president were to appear in a comic scene, it's going to be followed by unsubtle commentary on his performance as prez, for better or for worse.
Of course, that's not necessarily a bad thing. I happen to like Red Son and didn't take issue that they didn't exactly show a lot of reverence to Joseph Stalin, and certainly the story works better because they used the actual name "Joseph Stalin" and not some obvious stand-in. I guess, in short, I wouldn't say you should never use real politicians in your story, but I think it generally is unwanted.