> We have petitioned; we have remonstrated; we have supplicated; we have prostrated ourselves before the throne, and have implored its interposition to arrest the tyrannical hands of the ministry and Parliament.

Here we see that the conflict was not exactly about monarchy but about a parliament violating its jurisdiction. The colonies had their own legislatures. To the extent that the monarch did not correct the errors, sure, it was against monarchy.

Also from the date we see that the speech preceded Lexington and Concord by only a few weeks. But there was a powder raid in September of 1774 that caused alarm. April of 1775 was the start of of the war. Over a year later, the politicians drew up the Declaration of Independence.