“With the ability to play with gamers which are the perfect on the planet is an incredible alternative at such a younger age, and I need to be taught, develop and develop loads.
“I really feel like Chelsea is such an incredible setting to do this in.”
Chelsea's earlier switch file was the £900,000 they paid for USA defender Naomi Girma from San Diego Wave in January.
Thompson has scored six targets in 16 Nationwide Ladies's Soccer League video games this season. She has three targets in 22 video games for the USA.
Chelsea striker Mayra Ramirez has been dominated out till January with a hamstring harm, whereas England ahead Lauren James will miss the WSL season opener in opposition to Manchester Metropolis at Stamford Bridge at 19:30 BST on Friday.
