Why are there 2 distinctive versions of English, i.e. U.S. and U.K.?

Not like English isn't as complicated as it is already...

I was just looking at Sugi's whatsapp message. He mentioned an "installment" plan. I was pretty sure it's "instalment". But my HTC Android phone's auto spelling function came out as "installment"!

Of course, I was confused. I googled.

"Instalment" is how the English spell it.

Why can't we just have one universal way of spelling?! Ugh. Confuses me.

Tsk.

My guess is that the Americans don't really know how to spell, so it becomes generally acceptable since majority can't spell it the English way?

Must be.

O.o