I'm sorry, but what's the first and last instrument you hear, what's the only instrument playing through the first verse, and besides drums, what's carrying the bulk of the song?

I can't really. For example, I was convinced that Leah McFall's "Home" was going to be a hit because of The Voice and will.i.am's backing but it flopped. On the other hand, I didn't see Fancy, although I loved it from the get-go, doing any better than her previous UK singles had done.
Although all my friends think I can because I see what's smashing in America, introduce it to them, tell them it's going to be big and then it is

That happened to me, I was talking about All About That Bass in like July/August then they started playing it here in September, they must've thought I was psychic

I don't know but it just has something special to it that makes you wanna replay it all day. I predicted Fancy and 2 On would slay and they did, but then I predicted First Love would too and that, well.....

Same here!! I thought First Love would be at least Top 10

I knew some songs like Talk Dirty, Trumpets, Dark Horse would smash, and others like Turn Down For What, Show Me, Latch which I thought had potential. Others like Who Do You Love, Partition and No Mediocre I knew would do well.

Some did worse than I expected like Main Chick, Hideaway and 24 Hours (kind of). Rather Be I thought might have done better too.

And ones like Anaconda, Fancy, Hot Boy, All About That Bass did better than I expected at first.

a piano starts and ends alot of songs but that doesnt mean that they are "piano laden ballads" in the same manner as the other two you mentioned, where the piano is the primary instrument (Someone Like You or Stay). Just Give Me A Reason incorporates many synths and bass elements use by alot of Jeff Bhasker songs, Runaway by Kanye West included.....but this is a bit off topic so Ill just agree to disagree with you.

and as far as hit songs, usually the ones that smash incorporate new elements without sounding too different from the grand scheme of whats popular, and change in trends are usually gradual. The whole funk/dance of last summer was just a different take on the dance trend, as is the "white girl hip hop" which still takes various elements from the dance trend that seems in right now....similar to how in the previous decade, hip hop was on top, and timbaland along with others took that element and mixed it with dance, which in effect was a gradual progression to what we have today.

I can't predict what's gonna smash
I thought C'Mon and Somethin' Bad would do well.
I predicted Royals a few weeks before it blew up, and I'm still holding out for Riptide.

Bump.

check UK and Australian chart
if a song smash hard there, WW hit is coming.