The 27-year-old ended last season on loan at Bayern Munich, while earlier on in his career he played in Germany with Bayer Leverkusen.
Donovan is keen to return to Europe to secure first-team action ahead of next summer's World Cup finals in South Africa, with the USA drawn in the same group as England, Algeria and Slovenia.
Meanwhile, Toffees skipper Phil Neville is pleased with the progress he is making since his recent round of knee surgery.
He told the club's official website: "The rehab is going really well. It was a bad setback for me when I was told I needed an operation, but the surgeon did a fantastic job.
"He said I would be back in no time and since I woke up from the anaesthetic, my knee has felt great, better than it was before.
"I haven't been able to feel sorry for myself so I could fully focus on making sure the knee is really strong this time.
"I am the captain of the team and it is vitally important that I remain positive and pass that on to the others regardless of whether I am playing."
Source: DSG
