They were held for six hours at a police station before being charged with public order offences.
Mr McKenna, a member of the Spirit of Shankly supporters' club, which campaigns against the two Americans' ownership, said after the hearing: "I just shouted 'Yanks Out!'
"The police were out on their horses and they grabbed me. When I asked what for they said: 'For racism.'
"We were just there to make our point to the owners as we heard they were attending."
Malcolm Clarke, from the Football Supporters' Federation, said if true it would be of "grave concern".
He said: "This was clearly a protest against two particular people, not a general racist slur against Americans."
A spokesman for Merseyside Police said: "A 22-year-old man from Bootle was arrested for using threatening, abusive or insulting words or disorderly behaviour within the hearing or sight of a person likely to be caused harassment, alarm or distress and was subsequently charged with a public order offence.
"A 30-year-old man from Dingle was also arrested and charged for a section five public order offence.
"Both men were bailed to appear at North Liverpool Community Justice Court where the charges were discontinued."
Source: Telegraph
Source: Telegraph