The Swiss are looking into the controversial 2018 and 2022 World Cup soccer bids, which awarded the games to Russia and Qatar, respectively.
The Americans have outlined a case that sounds like a mafia movie script, with allegations of fraud, racketeering and money laundering over a period of more than 20 years. Several senior FIFA officials are among the defendants facing extradition from Europe, South America and the Caribbean.
"This really is the World Cup of fraud," said Richard Weber, head of the Internal Revenue Service's Criminal Investigation division.
Soccer is the most popular sport in the world, with 240 million people regularly playing the game, according to a FIFA estimate. Even in the United States, traditionally considered indifferent to soccer, interest is growing. More Americans watched last year's U.S.-Portugal World Cup game than watched the 2014 NBA Finals or baseball's 2013 World Series.
The bombshell announcement of the U.S. indictments was met with the sense that somebody was finally doing something substantial about the corruption allegations that have dogged soccer's global gatekeeper for years.
"We could make a case that this is the biggest sports bust in history today," USA Today Sports columnist Christine Brennan told CNN. "This is historic. This is monumental."
So, what comes next in the investigations?
Here are some of the key questions:
What will happen with the extraditions?
Seven of the 14 defendants wanted by U.S. officials were arrested Wednesday in Zurich, Switzerland, said U.S. Attorney General Loretta Lynch. The majority of them are contesting extradition to the United States, according to Swiss authorities.
The battle is set to play out in Swiss courts.
"I think there's a very good chance there will be extradition," said CNN legal analyst Paul Callan. He noted that Swiss authorities refused to extradite
filmmaker Roman Polanski to the United States in 2010, but Polanski's case is still rumbling on
in the Swiss courts.
"There are always outs under these extradition treaties," Callan said.
Extradition proceedings have also begun in Argentina and Trinidad and Tobago for defendants named in the U.S. indictment.
Are there more arrests in the pipeline?
U.S. law enforcement officials say they're not done yet.
The indictment unsealed Wednesday "is the beginning of our work, not the end" of an effort to rid global soccer of corruption, said Kelly Currie, acting U.S. attorney for the Eastern District of New York.
The people indicted Wednesday were all linked to soccer in the Americas, but it was unclear where the investigation might focus next and whom it might target.
Swiss authorities, meanwhile, are conducting their own investigation into bidding for the 2018 and 2022 World Cups.
The Swiss aren't as far along in their investigation as the Americans, but officials said they suspect criminal mismanagement and money laundering took place during the selection process.
Authorities raided FIFA's head office in Zurich on Wednesday, seizing electronic data and documents. Police plan to question 10 members of FIFA's executive committee who took part in voting in 2010 on the World Cup bids.
Will the Russia 2018 and Qatar 2022 World Cups be moved?
That still seems unlikely at this point.
FIFA has already announced the results of its own investigation into the bidding process for the two competitions, saying it found no corruption and had no reason to reopen the bidding process. (But Michael Garcia, the American lawyer who led the investigation, said FIFA's public summary of his report was "incomplete and erroneous.")
FIFA spokesman Walter De Gregorio said Wednesday that the two World Cups would go ahead as planned despite the Swiss investigation.
Holding the 2022 World Cup in the desert emirate of Qatar has already drawn criticism over the treatment of the migrant workers
laboring to build the stadiums for the competition.
Officials have also had to change the dates
of the tournament to the winter to avoid Qatar's sweltering summer heat, raising potential scheduling headaches for other soccer competitions around the world.
Qatar beat the United States and other nations in the bidding for the 2022 World Cup. Australia, one of the other countries to lose out, has been outspoken in its criticism of the tournament dates being switched.
Will FIFA's big election go ahead this week?
The arrests of FIFA officials in Zurich were rich in dramatic timing. They took place as representatives of the world soccer body's member associations were congregating in the city ahead of the organization's annual congress Friday.
The FIFA gathering, which this year includes a presidential election, appeared to have helped U.S. authorities by enabling them to have a large number of the defendants rounded up in the same extradition-friendly country.
The announcement of the U.S. and Swiss investigations prompted the executive committee of UEFA, European soccer's governing body, to call for the congress to be postponed and election to be held at some point in the next six months.
UEFA leaders said European soccer associations would have to "consider carefully if they should even attend this Congress" and would be holding a meeting Thursday to "decide on what further steps need to be taken to protect the game of football."
But FIFA's De Gregorio insisted Wednesday that the congress was sticking to its agenda.
The question is whether any of the other members or confederations will follow UEFA's lead.
Is Sepp Blatter going to win again?
Despite the scandal rocking FIFA, its incumbent president, who's held the top job for 17 years, appears set to maintain his grip on power.
Bookmakers still have Sepp Blatter as the firm favorite to defeat his only remaining challenger
, Prince Ali bin Al Hussein of Jordan, and secure a fifth term.
Blatter is not one of those arrested or facing charges from U.S. authorities, but he was among those investigated.
Asked if the U.S. investigation had cleared Blatter, Lynch said, "I'm not able to comment further on Mr. Blatter's status." Officials said earlier Wednesday that the investigation into Blatter's possible involvement continues.
The Swiss agency that ordered the arrests of the seven facing extradition to the United States does not plan to question Blatter for now, a representative of the office said.
The office "will not question Mr. Blatter as he is not one of those detained, or in custody, and we are the ones who are responsible for extraditing the people we arrested," the representative said Thursday.
Blatter is "calm" and "fully cooperative" with the separate Swiss investigation into the 2018 and 2022 World Cup bids, De Gregorio said.
"He is not a happy man, he is not saying, 'Everything's cool,' " but he is glad the process is taking place because it is good for the organization, De Gregorio said.
Ali said Wednesday that FIFA needs leadership "that accepts responsibility for its actions and does not pass blame. Leadership that restores confidence in the hundreds of millions of football fans around the world."
How are FIFA's lucrative sponsors going to respond?
Some of the biggest corporate names associated with soccer have already spoken out
In a strongly worded statement late Wednesday, Visa called on the world's premier soccer organization to "take swift and immediate steps" to clean up its act.
"It is important that FIFA makes changes now," Visa said. "Should FIFA fail to do so, we have informed them that we will reassess our sponsorship."
Earlier, another major sponsor, Coca-Cola, said the "controversy has tarnished the mission and ideals of the FIFA World Cup." The company said it has "repeatedly expressed our concerns about these serious allegations."
Other multimillion-dollar sponsors, including Adidas, McDonald's and Budweiser's parent company, Anheuser-Busch, also issued statements saying they were in contact with FIFA.
But it remains to be seen if any of them would go as far as severing ties.