To get the rewards, you must own shares by the record date, which is usually 1 business day before ex-dividend date. You will still get the dividend payment later if you sell shares after ex-dividend date.
The US Stock market’s instability depends on the state of the global economy. Strong global economies increase business profits and stock prices, while weaker economies may lead to low-profit rates and low stock values.
Moreover, fights between 2 countries over their economies can also impact their global trade by impacting their business and industries.