The meeting comes after Bobi Wine, who travelled to the US for specialised treatment, held a press conference in Washington DC alongside his lawyer Robert Amsterdam.
"Today, I met with @HEBobiwine and his wife, Barbara. During our meeting he underlined the importance of the democratic process as well as those who have and continue to suffer from political oppression in #Uganda. #PeoplePower #FreeZaake #Arua33," Mr Sherman posted on social media after the meeting.
Mr Sherman is serving as a Democratic member of the United States House of Representatives since 1997. He currently represents California's 30th congressional district within the San Fernando Valley, in Los Angeles County and the eastern Simi Hills in Ventura County.
Bobi Wine left Uganda for medical treatment in the United States following accusations he was tortured by security forces.
Kyagulanyi became an MP in 2017, firing up a youthful population and proving to be a thorn in the side of President Museveni.
He was charged with treason last month after protesters allegedly stoned Museveni's car during a by-election campaign.