"The Three Amigos" is a term often used to refer to the Presidents of the United States and Mexico and the Prime Minister of Canada, especially post-NAFTA.
In this case, it's referring to the three most recent Democratic Governors of California (Gray Davis, Jerry Brown, and Gavin Newsom, with 2003-2011 having seen a Republican, Arnold Schwarzenegger, in office).
Garrison is claiming that their policies, moving farther and farther left with higher taxes and even higher spending, are driving the state toward economic ruin, and that the Amigos are ignoring the warnings of the MAGA crowd.
Further, he claims that California is offering Central American immigrants "free stuff" with an open door in The Wall, and that they're harming the bear (on the state flag) with mandatory vaccinations, and that their strict gun control has effectively voided the Second Amendment within the state.
There's a sanctuary city in the distance, and the MAGA people are trying to escape the devastating tide by hiding behind rocks.