I don't think because of the USA will be among the host country of the FIFA World Cup that will make getting visa to be very easy , because if they make their visa to be very easy to get people will use it as a opportunity to gain access into the country. despite FIFA World Cup it will still be strict to get visa to USA.
The United States has experience of holding major sports tournaments, 3x holding the summer Olympics which also invites many people into their country, and being the second for the World Cup so they already understand very well how to reduce illegal immigrants who might damage security or who actually come there other than to watching football also has other intentions such as becoming an illegal worker, but making visa arrangements very strict will reduce the number of people who will watch the match while one of the income they are after from organizing this world cup is the presence of many spectators directly at the stadium, so I don't know what which they would do but would have had definite rules in place to keep everyone happy.