If every state does it differently, all that means is there'd be 52 numbers (allowing for Washington DC and Puerto Rico). A few minutes work with a pocket calculator. Not much longer with a pencil and paper. No reason they'd all have to do the count the same way.

And there' s no valid reason that a vote in each of the state needs to take longer than a couple of days, even where their population may be comparable to nations. As for counting votes by hand taking ¿weeks and weeks" - that's the way they do it in the UK, and the results are mostly done by the next morning, and every one in a coupe of days.

As I said, no need to count all the separate votes down the ballot, they could do the top one for President, and set the the ballots aside for the rest to be counted later.

It's not a matter of being limited by an antique Constitution or by the size of the country, it's about lack of the will to do it sensibly. Which I suppose is not surprising in a country where almost half the people voted for someone like Trump.