I feel like I’ve read plenty about the historical materialist understanding about how the US constitution was formed and its class characteristics, but a lot less about the actual act of declaring independence. I do know how a bunch of the founding fathers made fortunes from land speculation via genocide and stealing indigenous land; and how the Brits wouldn’t let the yanks do that because they didn’t want to start another incredibly expensive war with the native peoples. I’ve also read of Gerald Horne’s thesis about how the founding fathers were worried that GB would totally outlaw slavery. I have a lot respect for Horne, he’s great but frankly I think that theory has little to no concrete evidence supporting it. But those two are the only materialist analyses of independence that I’ve seen so far.
England had trouble managing a colony that was across the atlantic so they kept hiking up taxes to make it worth it. This pissed off the proto-bourgeoisie who liked having money, so the proto-bourgeoisie among the American merchants and planters decided to take a gamble and declare independence. Also the American ruling class wanted to expand westward into indigenous territory in spite of treaties the British crown had with indigenous tribes. Granted, it's not as though the British crown was going to honor those treaties forever, but the crown wanted to break those treaties on their own terms, when they thought it was the right time, while the ruling class among colonists wanted unfettered indigenous genocide, and the crown wasn't letting them have that.
So basically proto-booj complaining about "muh taxes and muh regulations"
EDIT: Your post says all this so I'm not sure I understand the question. There doesn't need to be much more to it.
The East India Trading Company in some ways had more power than King George at the time, commanding King George's decisions (which was helped along by King George's well-known personal issues which made him more susceptible to cunningly worded suggestions and pressure), too.
That company took and took and wanted its material losses pushed onto the colonies until the colonies' bourgeoisie (and their working class followers) pushed back.
Pre-modern corporations were still a fuck.
Fun fact, the Boston Tea Party happened because of lower taxes on tea. The American bourgeoisie were selling smuggled tea to avoid paying taxes and were pissed they couldn’t make bank anymore when the East India Company was allowed to sell cheaper tea.