All they needed was draw, righto?
No, not quite. A win put the US through outright. A draw means they either need a point against Germany, or to hope that the result between Ghana and Portugal goes their way (basically, the US goes through if it's a draw, Ghana wins by 1 goal and the US only loses by one goal or Portugal win without overturning a massive goal difference deficit).
The Portugal-Ghana game is likely either going to be a tie or a Portuguese win. The US is still going to be able to go through if they don't lose too badly and Ghana doesn't stomp. Portugal has basically an impossible situation here for them to advance.
I'm not sure why you think Ghana obviously can't beat Portugal, given that Ghana drew with the Germans whilst Portugal got stomped by them.
And, the US only goes through with a loss and a Ghanian win if you only lose by one goal, Ghana only wins by one goal and Ghana doesn't score more goals than you do. In that case, you'd go through on the head-to-head result. So, whilst it isn't certain that you'd go out if Ghana wins and you lose, there's a good chance.
On the other hand, a draw does put you (and Germany) through, and it is extremely unlikely that Portugal will catch up the goal difference, so anything other than a Ghanian win does pretty much mean you're through, yes.