What was the main reason why the U. S.
wanted to become an "empire" and
expand it's control?

c. had saved colonel cresap's family from attack by other native americans.

so, based on the research i've done. the u.s. government were always on a wild goose chase just to take down castro. he then retired his trone to his brother raul in 2008 due to some health issues. so it's obvious your answer would be:

castro had no allies from which he could receive aid.

hope this and have a fantastic day!

                                                    -wolfiewolffromsketch