Players from both Jacksonville Jaguars and the Baltimore Ravens dropped to their knees as the national anthem was played prior to the match in London. Now similar protests have erupted across the US with at least 100 players either kneeling or sitting during the national anthem.
No players were kneeling during the playing of 'God Save The Queen' at Wembley, which followed the Star Spangled Banner.
They did so after President Trump stoked tensions by saying NFL players who protested during the national anthem should be sacked by their team.
At a rally on Friday night the president said: 'Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, to say, 'Get that son of a bi*ch off the field right now... he is fired.'
He was referring to a controversial string of protests started by player Colin Kaepernick last year when he sat or kneeled during the anthem to highlight the treatment of black Americans.
Players on both teams playing in London and Jaguars owner Shad Khan, who were not kneeling, remained locked arm-in-arm throughout the playing of the national anthem and 'God Save The Queen'.
Khan, who also owns Championship football club Fulham, has previously donated one million US dollars to Trump's presidential inauguration.
Shortly after the contest got under way at Wembley, the Ravens posted a message on Twitter which read: 'We recognise our players' influence. We respect their demonstration and support them 100 per cent. All voices need to be heard. That's democracy in its highest form.'
The Jaguars tweeted a photo of Khan standing, arm in arm with Lewis and Smith, with the caption 'Unity'.
The team's owner, Steve Bisciotti, added that he '100 per cent' supported his players' decision to kneel.
'We recognize our players' influence. We respect their demonstration and support them 100 per cent. All voices need to be heard. That's democracy in its highest form,' he said.
The Wembley protest was the first in a series organised by NFL teams disgusted with Trump's comments.
Games kicked off across the States with unprecedented numbers of players taking a knee during the Stars and Stripes.
Players from the Seahawks and Titans both remained in their locker rooms during their game in Nashville.
All of the Pittsburgh Steelers players stayed in their locker room as the national anthem was played before their match against the Chicago Bears. Only the Steelers coaches, including head coach Mike Tomlin, were on the field for the anthem.