I don't agree that there is too much punctuation, but some of it is wrong!
To my mind there should not have been a comma in the first sentence, but a semi-colon after "the whole country" would have been preferable to the comma there.
A letter of this kind should not contain dashes and commas instead of repeating "and" all the time when listing their accomplishments would have been an advantage. Why "seemed to shine" instead of simply and less demeaningly "shine"?
Whoever wrote it needs to pay attention to punctuation, style and learn to re-write a letter if he or she has forgotten the first sentence, not just add it as a hand-written emendment.
If the hand-written salutation was intended to make the letter look as if it had actually been written by Boris Johnson himself, it doesn't work. Only an entirely hand-written letter would create that impression.