When Chicago lost the bid for the 2016 Olympic Games, some speculated that America’s strict visa policies were to blame.

Hours before Rio de Janeiro won the Olympics, one member of the International Olympic Committee called the process of entering the United States "a rather harrowing experience". Not surprising since the US is one of the hardest countries in the world to enter.

Whether or not border control affected the 2016 bid is up for discussion. But concerns surrounding tourist visas certainly do come into play during major world sporting events. During the last Summer Olympics, in Beijing, China doubled the price of tourist visas, making it even more difficult to cross its borders. And while the next two Olympic hosts, London and Rio de Janeiro, are not likely to impose added burdens, visiting these cities will still be difficult for certain passport holders.

The European Tour Operators Association expects the number of tourists to London during next year's Summer Olympics to be far lower than expected, in part due to visa restrictions which it calls "surly and alienating". Some passport holders, for instance, must have fingerprints taken, sit for interviews, and pay 70 pounds before even finding out if their visas have been approved.

More than 100 countries require visas to visit the UK. All countries except these 67 require visas to visit Brazil. Why is it that certain nationals require visas to certain places while others do not? Visas, or permits allowing people into foreign countries, are used by governments to document, restrict and control who is inside their borders and for how long. Visa applications, interviews and fees can all create obstacles to entry. And visas tend to be the most prevalent for citizens of developing nations, especially those struggling with war or repression. A study last year, for example, found that while citizens of the UK enjoy visa-free travel to 166 countries, citizens of Afghanistan can only visit 26 countries without first obtaining visas.

Countries with strict visa rules have a number of reasons for wanting to secure their borders. Some want to keep terrorist suspects out; some want to keep disease out; and some want to keep political foes out. While some nations charge steep fees and have long processing times for visas, others present even more hoops to jump through. Russia, for instance, requires tourists to obtain letters of invitation. This may increase visa stress in 2018, when Russia hosts the FIFA World Cup – especially because Russia already requires tourist visas for nationals from the vast majority of countries.

Sometimes one country's visa policy is developed in reaction to another's. For instance, since the US charges Brazilians hefty visa fees, Brazil charges Americans "reciprocity fees". Any US citizen hoping to visit Brazil for the 2016 Olympics, or for the more imminent 2014 FIFA World Cup, can look forward to paying about $160 and waiting about two weeks to get a visa. It's Brazil's way of standing up to America's strict policies; but it could negatively affect tourism during two of the country's biggest sporting events of all time.

As host countries invest in preparations for the Olympics and the World Cup, they can only hope that visa policies won't scare tourists away. If the sporting events do boost tourism, as hoped, these countries may have to work hard to ensure that the influx of visitors won't cause visa applications to bottleneck. Because, if problems ensue, they may not be asked to host the next time around.

Travelwise is a BBC Travel column that goes behind the travel stories to answer common questions, satisfy uncommon curiosities and uncover some of the mystery surrounding travel. If you have a burning travel question, contact Travelwise.