Here is what Trump's National Security Advisor had to say about a possible US withdrawal from the Open Skies Treaty in 2019:
“American withdrawal would only benefit Russia and be harmful to our allies’ and partners’ national security interest.”
“...Ukraine in particular, have repeatedly stressed the importance of the Open Skies Treaty for their efforts to monitor Russia’s military.”
On November 2, [edited] 2021, Putin's employee, losing President Donald Trump withdrew from the Open Skies Treaty.
But gosh, Biden is so weak!