Donovan frustrated by disallowed goal
The US game was controversial
USA looked to be in major trouble at half-time as Valter Birsa and Zlatan Ljubijankic had put Slovenia in a commanding position, but Donovan fired home shortly after the break before Michael Bradley grabbed an 82nd-minute equaliser.
However, it appeared USA should have come away with a 3-2 win after Edu's 85th-minute strike was controversially ruled out, and Donovan feels there was little justification for the decision.
"I'm proud of our guys," he said. "I don't think there's many teams that would respond that way after going 2-0 down [but] I'm a little gutted, to be honest. I don't know how they stole that third goal from us. I'm not sure what the call was. I don't know."
On referee Koman Coulibaly, he added: "It was the guy's first World Cup game, so maybe he got a little caught up in the moment, but you can't take a perfectly good goal from a team, especially at a World Cup.
"When we asked him several times, in a non-confrontational manner, why he made that call, he just ignored us. Maybe he didn't understand us since I don't know how much English he speaks."
Coulibaly, from Mali, has previously officiated at several African Nations Cup tournaments and was in charge of the 2010 African Nations Cup final between Ghana and Egypt.
Donovan, though, believes USA should not have allowed themselves to go two goals down in the first place. "We know we're good enough to play against a team like that," he said. "We can't keep putting ourselves in holes like that. We've got one more chance against Algeria, and we're still alive."
USA coach Bob Bradley echoed Donovan's thoughts on the disallowed goal. He said: "In the midst of a game and everything that's going on it's rare that when a tough call is made that the referee will give you an answer.
"Sometimes, after the fact, you get an answer, and sometimes that's not the case either. Sometimes you are frustrated because you feel that situations have not been handled 100% correctly or fairly, but that's the way the game works and you move on."
He added: "On the set-piece most of what took place was Slovenia players holding our players.
"A Slovenia player had his arms round Michael (Bradley, the coach's son), Michael tried to break clear and the foul was called. There might have been three fouls in the box, all of which were by Slovenia players."
Slovenia coach Matjaz Kek was happy with the performance but disappointed not to have taken the three points after going 2-0 up.
"I am really proud of my squad but, yes, there is some aftertaste of expectations not having been met," he said. "We were ahead of the US and we didn't overcome this pressure.
"There is pride and enthusiasm and maybe just a bit of disillusionment. This is a match we will learn from."
Slovenia next face England in Port Elizabeth on Wednesday but Kek refused to look ahead to the match at this stage.
"We are not considering our match against England at this point. My priority is to have my squad recovered - they have expended a lot of energy. We need to recover and then we will talk about England. It's very clear what we will be up against."