The final line of the Monroe Doctrine sort of sums up Monroe's arguments…in a somewhat passive-aggressive way.

He says that the U.S. will leave the newly independent nations down south to determine their own governmental structure, and he hopes that other countries will do the same. It's the early 19th-century presidential address equivalent of leaving a note for your roomie that says, "Some of us have to get up early. Some of us don't have time to listen to 90s hip hop at 3 a.m."

Anyway, the Monroe Doctrine ends with a firm statement that the United States intends to let the Latin American republics determine their own policies and governments, and wants to lead by example in doing so. The thinly veiled subtext, especially looking at the rest of the paragraph, is that these new countries have chosen, and will continue to choose, a republican system like the U.S. European countries shouldn't try to come in and re-institute the monarchical colonial systems that these places literally just rebelled to get away from.

To sum up: follow the United States' example and let those new countries alone so they can choose the American way.