Ganna of Ineos completed the course around the city of Valladolid in 27 minutes and 39 seconds, although exhausted mountain specialist Kuss still leads the overall standings by 26 seconds from Spaniard Marc Soler.
Belgian Quick-Step rider and defending champion Remco Evenepoel raced in his time-trial world champion rainbow jersey and was 16 seconds slower than Ganna in second on the day.
He is now third overall at one minute and nine seconds and crucially extended his lead over Primoz Roglic to 27 seconds and Jonas Vingegaard by over a minute.
"It's great to be here on such a lovely day and win another stage after I also won at the Giro," said Italian Ganna.
"Let's see what else we can do. I'm here to help 'G' (Geraint Thomas)."
Evenepoel beat Ganna to the world title in Glasgow last month but explained he suffered a blip here.
"I think it's pretty good. Knowing that I didn’t have the best TT legs today," said the Belgian.
"We have to be happy with the general classification gaps that I took today and coming quite closer to Sepp who actually did a super good TT. So hats off to him."
Kuss is riding as Jumbo's third man, complicating tactics for Evenepoel as he faces a triple challenge to his title from the Dutch team.
As provisional leader the slender Kuss, who is by no means a time trial specialist, was delighted to retain his lead after embarking as the final rider in the individual run.
"I started last so it's the first time nobody has overtaken me in a time trial," he jested. "It was something different for sure, a new challenge for me," he said.
Roglic is in fourth and was all smiles as he warmed down after the race, while French rookie Lenny Martinez remains fifth and is expected to do well in the mountains ahead.
Wednesday's stage 11 from Lerma to La Laguna Negra ends with what should be a hotly contested 6.5km climb to the finish.
