Brexit Vote Tanks Markets, Trump Talks Brexit, 20 Killed In WV Flooding

Britain's stunning vote to leave the European Union is both historic and world-changing. But what does it really mean for folks living on the other side of the Atlantic? Potentially, everything -- the economy, national security, even the race for president. Here are five ways Brexit will affect Americans:

It could hurt the economy.

The UK is the world's fifth-largest economy and one of the United States' largest trading partners, so if it catches a cold, we may get a little sick, too. When the pound dropped to 30-year lows as the results came in and British stocks got pounded, it was no surprise when Wall Street tumbled more than 500 points right after the opening bell Friday morning. So yes, your 401k's probably a little smaller right now.

Lots of U.S. companies invest in the UK as a gateway to the rest Europe's market. Companies like Rolls Royce and JPMorgan warned before Thursday's vote that leaving the EU would put those investments and jobs in the UK at risk. Big companies and banks may also move staff to Germany or France to avoid disruption to their EU business. Why's that risky for the U.S.? There's a real fear that increased unemployment in the UK and all the uncertainty could push Britain into a recession, and it could take America's economy down with it.

David Cameron falls on his sword as gamble backfires.

Has David Cameron's decision to gamble the future of the United Kingdom left his political career in ruin?

It was a move that backfired spectacularly and led to the dramatic announcement that he'll quit as Britain's prime minister in the aftermath of the Brexit vote -- an era-defining moment that will no doubt lead to him being remembered for generations to come as the man who took the country out of the European Union.

For a man who told members of the Conservative Party to stop "banging on" about Europe in his first conference speech as leader, it is perhaps fitting that his reign comes to end with such symmetry.

Outside 10 Downing Street Friday, Cameron, who had defiantly championed the cause of the Remain campaign, conceded that his position had become untenable after a night of drama.