800 is the capacity of St. George's Chapel, so H&M were somewhat conservative in keeping their guest list at a minimum. The public invitees allowed in side the gates of Windsor Castle are specifically outstanding contributors to their communities across Britain, as well as some members of Harry's charities. The wedding invitations were printed with American ink on British paper.
The whole politics brouhaha the royals have wisely decided to completely avoid. I doubt the royal family are fans of PM Theresa May, so she was unlikely to be invited in any case. Plus, I'd heard that May brought up the politics issue after the engagement unnecessarily. May was reported to have said that the Obamas should not be invited if Trump and/ or a family member was not also extended an invitation, which is stupid. I doubt Harry and Meghan appreciated May placing an unwelcome focus on politics in the immediate aftermath of their engagement.
No U.S. politicians were invited to William/Kate's wedding in 2011. W&K's wedding also was not considered a state occasion. It's just that William is heir to the British throne and he was also married at a larger venue (Westminster Abbey). The initial guest list drawn up for W&K's wedding was disliked by W&K. So it's been reported that Queen Elizabeth told them to tear it up and make out their own list, and that she would deal with any political/ diplomatic fallout. A number of people in the British government were not invited to W&K's wedding but there were some Commonwealth heads of state who were invited. Before they were married in April 2011, W&K had never met the Obamas, so they did not invite them to their wedding. However, in May 2011, Queen Elizabeth hosted the Obamas in London at a state dinner. I doubt that U.S. Presidents are usually extended British royal wedding invites in any case. In 1981, Nancy Reagan attended the wedding of Charles and Diana, but President Reagan was not there.
I can bet that Trump and crew will not anytime soon (and hopefully never) be invited to a state dinner at Buckingham Palace. Meanwhile KP press office made sure to mention that Prince Harry and Meghan will be meeting with the Obamas at some point soon, and that both couples are looking forward to getting together. The announcement of no politicians at Meghan/Harry's wedding indicated that the Royal Household in consultation with the UK government made the decision that no politicians were needed to be included on the invite list. The current contentious and volatile political climate surely has a lot to do with the decision to avoid political-related wedding guests.
OTOH, I believe if it had been left up to Meghan and Harry, both the Obamas and the Trudeaus would have been on their wedding guest list. Meghan is close to Sophie Trudeau and she also knows Justin Trudeau. Harry is also friendly with the Trudeaus. Sophie Trudeau spoke at the Invictus Games ceremonies in Toronto last September. Obviously, Prince Harry has a friendly camaraderie and charitable working relationship with both Barack and Michelle Obama. By this point, Meghan may have met at least President Obama, if not yet Mrs. Obama. A lot goes on behind palace walls and there are surely many private gatherings that the public never knows anything about, unless it's revealed by the royals themselves.
For example, Harry & Meghan revealed in their engagement interview that Harry had introduced Meghan to Diana's family and friends. Earl Spencer tweeted in November about having received an American wine for Thanksgiving, which gives the impression that Meghan and Harry enjoyed Thanksgiving with the Spencers at Althorp last November. It's reported that Harry's Spencer relations have all been invited to the wedding.
Re the cake (not a traditional British fruitcake):
https://twitter.com/kensingtonroyal/status/976039352605335553?lang=en
Flowers:
https://twitter.com/kensingtonroyal/status/980357967055814657?lang=en
