I hate to disrupt your response by throwing out "facts" but here you go:
http://futsal.com/teams/ That will take you to the home of USFF which is the ONLY association that falls under the US Soccer Federation reach and therefore the ONLY one that can call itself a US National Team. Now that we are on a roll with facts lets check out:
https://www.usyouthfutsal.com/programs This is US Youth Futsal and you'll see they have an Academy and Educational piece just as i referenced above but NO NATIONAL TEAM. They can call it a US Youth Futsal National Team all they want but without the USSF stamp they cannot and will be considered a United States national team.
In regards to clubs and league there but a few leagues or club and each of them represent a smaller number of teams that your local AYSO region has. I'm more interested the roll out of a real league.
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