A lot of automakers in the USA get subsidies, GM even got bailed out in 2008.
Tesla on the other hand creates a lot of jobs, invests in US factories, invests into R&D, pays a lot of taxes, and most importantly - delivers on the vision of transition to clean energy.
Without Tesla, America would still be driving even more gas guzzling SUVs and pickups.
So the relationship is mutually beneficial for the company, country, economy, and ecology