Welcome to FT!

Assuming you have already earned the bonus in your Citi AA card and is somewhat well padded, you should be all set for travel to South America. Go in off season so it's even cheaper on the miles. For Asia, I would add another $2k to your spend (total $10k) and get the Citi ThankYou Premier, Prestige, and Chase Sapphire Preferred. This would net you 140k points outright, 10k additional for the spend, and 5k additional if you add a second user to CSP. Transfer to SQ and you could be in Suites. Maybe some positioning flights. Like you say, the possibilities are endless but be sure to jump on one of the Citi cards mentioned. Good luck!