Manuel Pellegrini is reportedly keen on signing the 26-year-old to bolster his options at centre-back.
Premier League clubs must submit their applications before the transfer window closes on Thursday.
"As our biggest ally, it seems strange that a football player from the US can't automatically get a work visa to play in England," Long told Sky Sports.
West Ham have five days to secure a work permit for USA international Aaron Long— Sky Sports Premier League (@SkySportsPL) August 3, 2019
"Every kid in the USA dreams of playing in the English Premier League.
"Not many players get the chance, so of course I would like to play there some day."
Multiple Ligue 1 clubs including Marseille have been linked to Long, the MLS Defender of the Year for 2018.
"I just signed a new contract, so the decision is up to my club and the other team," he said.