I would think that worldwide, since soccer is the most popular sport, a soccer team would dwarf the popularity of any US team. So for that I would say either Manchester United or Real Madrid.
But in the US and for anyone who pays the least bit of attention to US sports, Yankees would win hands down.
You mean to us or internationally?
I would have to say the Lakers internationally. Euros may dislike our football and baseball, but they worship the ground Kobe walks on.